NRLF
B ^ S3E 5D3
'\\
LIBRARY
UNIVERSITY OF
CALIFORNIA SANTA CRUZ
UNIVERSITY OF CALIFORNIA.
FROM THE LIBRARY Ol
BENJAMIN PARKE AVERY
GIFT OF MRS. AVERY.
August, 1806.
Accessions No.
METEORS,
AEROLITES, STORMS, AND ATMOSPHERIC PHENOMENA.
FROM THE FRENCH OF
ZUECHEK AND MARGOLLfi.
BY
ILLUSTRATED
WILLIAM LACKLAND.
BY LEBRETOJf.
NEW YORK:
D. APPLETON AND COMPANY, 90, 92 & 94 GRAND STREET.
mo.
ENTBKED, according to act of Congress, in the year 1869, by
D. APPLETON & CO.,
in the Clerk's Office of the District Court of the United States for the Southern District of New York.
M27/3
PRBF AC E.
THE nations of antiquity contemplated the grand spectacles that Mature offers with emotions different from ours. Their admiration partook more largely of amazement and fear.
We read in the Vedas, or sacred books of India, the following sentences :
" Will the sun rise again ?
" Will our beloved aurora return ?
" Will the powers of the night be conquered by the god of day ? "
To us these questions seem strange. Were they put in earnest ? Were the men of the ear- liest ages serious when they asked themselves anx- iously at night whether the light of day would overcome the darkness, and reappear at dawn to restore sunshine, heat, and life, to the world ?
4: PREFACE.
Yes, there is no doubt of it ; history attests the fact ; the earliest nations thought that the stars were animated, living bodies. In their eyes the heavenly bodies were superior beings, good or bad deities, friends or enemies, and ever ready to engage in conflicts of which the issue might be favorable or injurious to mortals.
The Aurora, or Dawn, itself was one of these divinities, and the most charming of them. Al- ways beautiful with freshness and youth, she was ever saluted and hailed with gratitude, because she it was who came the first to announce the de- feat of the powers of darkness and evil, and each morning, like a tender and faithful messenger, awoke the sons of men.
It is not with these childlike feelings that we moderns contemplate the sublime scenery of cre- ation. We never entertain a doubt in our day of the regular reappearance of the sun ; we know beforehand the hour, the minute, nay, the very second of his rising, and we can calculate with precision the length of the dawn in different climes. But this happy certainty, which we owe to science and experience, has not weakened the
PREFACE. 5
sense of admiration in our souls. On the con- trary, this religious and prolific feeling has in- creased in strength, in elevation, and has become more and more chastened as reflection and study have gradually revealed to us, with greater force of testimony, the infinite power and goodness, of the Great Being who presides over the universe. "We follow with an interest full of poetic thought the progress of the human mind in the study of these natural forces, these material agents, these vast springs of life and motion, that obey the will , of God, and of which the ancients had only sa confused an idea. How vast a field is here opened to observation, even when limited to the phenomena which have merely the terrestrial at- mosphere for their theatre ! "What a variety of effects are produced around us by the action, and by the incessant combinations, of the three ele- ments— air, fire, and water* — which serve to maintain and develop life in all its grades and in all its forms on the surface of the globe !
It has been said with truth by Ernest Faivre,
* Atmospheric phenomena are usually divided into aerial, aqueous, or igneous meteors.
6 PREFACE.
in his book entitled " The Scientific Works of Goethe : " " The spectacle of the various condi- tions of the sky ; the changing aspects of the clouds, the rain, the hail, and the tempest, as they form above our heads ; the appearance of luminous meteors, such as the aurora borealis, the halo, and the rainbow, have in them some- thing marvellous that enchains attention ; and for an intelligence capable of deep appreciation such studies must have a resistless charm."
CONTENTS.
CHAPTER I.
THE ILLUMINATION OF THE ATMOSPHERE. — TWILIGHT. — THE MIBAGE.
The Atmosphere.— The Azure Vault of the Sky.— The Prolongation of Daylight.— Colors of the Spectrum.— Twilight in the Polar Regions.— The Anti-Twilight.-The Mirage.— The Fata Morgana 13
CHAPTER H.
CLOUDS AND FOGS.
The Clouds.— Formation of the Clouds and Mists.— Influence of the Ma- rine Currents. — Extraordinary Fogs. — Appearance and Motion of the Clouds.— Hail-Clouds.— Forms of the Clouds.— Cloud-Rings.— Influ- ence of the Mountains.— Distribution of the Clouds.— The Spectre of the Brocken.— The Shadow of Mont Blanc... .. 34
CHAPTER III.
BAIN, SNOW, AND HAIL.
Dew.— White Frost.— The Distribution of Rain on the Surface of the Globe.— The Great Rains of India.— Regions without Rain.— Influ- ence of Forests.— The Softening of Climates.— Forms of the Snow.— Flowers under the Snow.— Glaciers and Rivers.— Hail ... . . .61
8 CONTENTS.
CHAPTEK IV.
PHENOMENA OF THE GLAOIEBS.
Meteorology of the Glaciers.— Their Formation.— The Grindelwald and Furca Glaciers. — Amphitheatres. — Neves. — Moraines. — Movements of the Glaciers.— Primitive Glaciers.— Polar Glaciers.— Variations of the Seasons and Climate . . 86
CHAPTER V.
THUNDER- STORMS.
Luminous Phenomena.— The Fires of St. Elmo.— Thunder-storms among the Mountains. — The Forms of Lightning. — Globular Thunder- bolts. — Thunder. — Singular Effects of Lightning. — Lightning-rods. — Geogra- phy of Thunder-storms. — Influence of the Soil. — Volcanic Storms. — Action of Thunder-storms upon the Subterranean Waters. — Utility of Thunder-storms , .. 101
CHAPTER VI.
WHIRLWINDS.
Water-spouts.— Electric Whirlwinds.— Sand-storms.— Water-spouts at Sea. — Water-spouts on Land. — Tornadoes. — Cyclones. — Hurri- canes 139
CHAPTER VII.
RAINBOWS. — CROWNS, AND HALO8.
Description of the Kainbow.— Play of Light in the Drops of Water.— Varied Appearances of the Arch.— Supplementary Arcs.— The Cir- cles of Ulloa.— Crowns.— Colored Arcs.— Parhelia.— White Arcs.— Anthelia.— The Halo of Clere ... . . 170
CONTENTS. y
CHAPTER VIII.
THE ATTOOBAL LIGHTS.
General Description.— Icy Fog.— Noise and Odor.— Electrical Currents. —Magnetic Influence.— The Aurora Australia.— Different Points of View.— Periodicity of the Auroral Lights 190
CHAPTER IX.
SHOOTING-STABS.
Fire-balls.— Showers of Stones.— Meteoric Stones.— An Extraordinary Meteor.— Velocity and Appearance of Fire-balls.— The Fall of Aero- lites.—Periodical Reappearances.— Composition of Aerolites.— Dark- ening of the Sun.— Ring of Meteorites 207
CHAPTER X.
DUST IN THE ATMOSPHEBE. — DBY TOGS.
Cosmic Dust.— Volcanic Ashes.— The Sands of the Deserts.— The Red Mists of Cape Verde.— Showers of Manure.— Dry Fogs 235
CHAPTER XI.
PBOGNOSTIOS OF THE WEATHEB.
Progress of Meteorology. — Foretelling the Weather. — Orpheus, Ho- mer, Hesiod, Virgil. — Prognostics furnished hy Animals. — Prognos- tics from Plants, and from the State of the Sky.— Characters of the Seasons and of Future Tears.— Shooting-Stars.— Influence of the Moon 261
CHAPTER XII.
PBAOTIOAL METEOBOLOGY.
The Brussels Conference.— Meteorological Practice. —Instruments of Observation.— Telegraphic Meteorology.— The Hurricane of Decem-
10 CONTENTS.
ber 2, 1863. — Alarm-Signals. — Rural Meteorology. — Association for the Advancement of Meteorology 286
NOTES.
INSTRUMENTS OF OBSERVATION.
The Barometer. — The Thermometer. — The Hygrometer. — The Pluvi- or Udometer 319
LIST OF ILLUSTRATIONS.
PAGE
THE MIBAGE, 25
FATA MOBGANA, 30
CIEETJS AND STEATUS, » . 48
NIMBUS AND CUMULUS, 49
SPEOTEE OF THE BBOOKEN, 55
SHAPES OF SNOW-FLAKES, 77
THE LYSE-FIOBD, 131
A VOLCANIC STOEM, 133
A WATEB-SPOUT, 148
A HUEEICANE, . . . • • , .163 A BAJNBOW, ..... . . . 170
WATEBFALL EAINBOWS, 173
THE CIECLE OF ULLOA, 178
HALOS, 182
THE AUEOEA BOEEALIS, 190
THE HUEWOETH METEOE, 214
SHOWEE OF SHOOTING-STABS, 227
A WILL-O'-THE-WISP, 255
THE STOEM-GLASS, 294
ALAEM-SIGNALS, 306
THE PLUVIOMETEB, 323
METEORS AI^D METEORIC PHENOMENA.
CHAPTER I.
TEE ILLUMINATION OF THE ATMOSPHERE.— TWILIGHT.— THE MIRAGE.
The Atmosphere.— The Azure Vault of the Sky.— The Prolongation of Daylight.— Colors of the Spectrum.— Twilight in the Polar Regions.— The Anti-Twilight.— The Mirage— The Fata Morgana.
THE ATMOSPHERE.
" THE atmosphere surrounds the earth with a spherical envelope, or wrapping, the thickness of which is unknown.1
" However, numerous observations have indi- cated that the limit of this atmospheric envelope cannot be either less or more than a little over sixty-two miles.
" This atmosphere, although invisible, presses on the surface of our bodies at the rate of fifteen
1 It will always be impossible, perhaps, to attain a rigorously accurate estimate, because the rarefaction of the upper layers augments precisely as the height is greater and the pressure less.
14 METEOKS AND METEORIC PHENOMENA.
pounds per square inch, so that each of us carries about, without feeling it, a total weight of nearly 35,000 pounds.
" Lighter than the lightest down, less palpable than the most delicate filaments, it leaves intact the spider's web, and hardly bends upon their stalks the flowers that it refreshes with its dews ; yet it bears with it around the world the ships of all nations on its wings, and crushes the hardest rock or metal with its weight. When in motion, it is strong enough to uproot the loftiest trees, and overturn the most substantial monuments, to toss the ocean in furious billows, and shatter the proudest vessels as though they were but toys.
" The atmosphere heats and cools, by turns, the earth and all the creatures that inhabit it.
" It drinks up the mists which it holds aloft in overarching clouds, and then showers them down in rain or dew upon the thirsty ground.
" It refracts and reflects the rays of the sun, in order that it may give us dawn and twilight, and make the heavens glow with dazzling colors when the great luminary rises and sets.
"Were it not for the atmosphere, the sun would come to us and leave us abruptly, and we should pass without transition from the gloom of midnight to the blaze of noon. We should no
THE ATMOSPHERE. 15
longer enjoy the soft radiance of twilight, nor would the clouds any longer shade the earth to protect it from the burning heat of the day.
" The atmosphere brings us the elements that sustain the flame of life, as they do the fire on the hearth ; and it receives and transmutes in its breast all the deleterious substances thrown off by decomposition. By its circulation it brings us all together in a common life of interchange and mutual dependence. A gaseous substance which would be fatal to us, to wit, the carbonic acid which we constantly inhale and throw off, it dis- perses over every part of the globe.
" The date-palms of the Nile, the cedars of Lebanon, the cocoa-nut-trees of Tahiti, imbibe it to improve their growth, and the palms and banana- trees of Japan transform its poisonous breath to flowers. That healthful substance, the oxygen which we breathe, comes from the magnolias of the Susquehanna ; the splendid trees that fringe the Amazon and Orinoco; the giant rhododen- drons of the Himalayas ; the roses and the myr- tles of Cashmere ; the cinnamon-trees of Ceylon, and the ancient forests that stud the interior of Af- rica. All contribute to supply the agent of life." *
1 See Dr. Buist, in the Transactions of the Bombay Geographical Society, vol. ix., 1850.
16 METEORS AND METEORIC PHENOMENA.
THE AZTJRE VAULT OF THE SKY. THE PROLONGATION
OF DAYLIGHT.
The uppermost regions of the atmosphere are not illuminated by daylight. They are given over to eternal night. At a certain height, we begin to see the diffused radiance produced by the parti- cles of the air acting on the rays of the sun, like the thousand facets of a crystal, gradually die out. To the eyes of aeronauts at the height of eight or ten thousand feet above the earth's surface, the stars seem to be shining through the deepest night, while beneath them the earth is glowing with the sun. The beautiful blue tint that appears to us to belong to the sky itself is really only that of the air beheld in masses. It grows darker above the luminous region that immediately sur- rounds us.
The vault that we seem to gaze upon does not exist. The atmospheric layers, augmenting in density as they approach the terrestrial surface, lend this deceptive appearance to the sky. It took a long time to overcome this illusion, and to establish the fact that the form and the dimen- sions of the celestial vault change with the condi- tion of the atmosphere, its opaqueness or trans- parency, and its greater or less degree of illumina- tion.
THE AZURE VAULT OF THE SKY. 17
The rays of the sun are partly extinguished in the air through which they pass. Their dim- inution is much less at the zenith than at the horizon, where they have to traverse a layer of the atmosphere fifteen times as thick. Thus we can fix our gaze upon the great luminary without be- ing dazzled when it has just risen. A modifica- tion of the same nature takes place in terrestrial objects which are less and less easily seen as their distance augments — " ' tis distance " " robes the mountain in its azure hue."
This tint so peculiar to the atmosphere is fre- quently altered by the watery particles which it contains, and which generally throw off white light ; this serves to explain the variations observ- able in the sky where the blue is more decided at the zenith than at the horizon. The color of the same part of the sky often changes in the course of the day. It grows deeper and deeper as we advance from morning until noon, and then insen- sibly fades until evening.
A very simple experiment will assist us in comprehending that property of light which is called refraction. Put a penny on the bottom of a wide empty vase, or basin, and step back until the coin is hidden from your view ; then, with- out changing your position again, you will see the
METEORS AMD METEORIC PHENOMENA.
penny come into view whenever some water is poured into the basin. This is because the light follows a broken line, and the same thing happens whenever it has to pass from a volume of air of greater to one of less density. In like manner may we explain that other phenomenon of the at- mosphere which, by refracting the rays of the sun, causes us to see it at a greater elevation than the real one, and thus perceptibly increases the length of the day.
Before rising, the sun illuminates the higher ranges of cloud, and they reflect his light to us. This light gradually increases until his disk ap- pears. The directly opposite effect takes place in the evening, when the sun is setting. Who has not often admired those successive transitions, those struggles between day and night, that offer so sublime a spectacle, endlessly varied by the thou- sand colors of the vapors spread along the horizon, and the clouds that float in the sky ?
THE COLORS OF THE SOLAR SPECTRUM.
If we cause the solar light to pass through a prism of crystal, it produces a colored spectrum. This spreading forth of different hues, which has an almost magical effect, is produced by the de- composition of a white ray into several kinds of
THE COLORS OF THE SOLAE SPECTRUM:. 19
light, of which the seven principal hues follow each other in the subjoined order :
Violet, indigo, blue, green, yellow, orange, red.
That property of the atmosphere which pro- duces this phenomenon is designated in science by the name of dispersion.
Mr. Forbes, an English physiologist, has made and described a very curious observation of the play of light in vapors suspended in the air. This observation assists us in comprehending the phenomena visible during the morning and even- ing twilight.
Mr. Forbes was standing near a locomotive that was about to start, and was looking at the image of the sun reflected in the column of steam that issued from the 'scape-pipe.
Immediately over the orifice, the vapor was clear and transparent like the air. The sun's rays passed it without diminution of strength, and fell upon a white wall opposite. A little higher up, the light appeared less vivid, but the color was orange, and the half shade thrown upon the wall reminded the observer of the first tints of evening. The disk of the sun just above it was of a deep- red color. Beyond that the steam, before resolv- ing itself into drops of water, would not allow
20 METEORS AND METEOKIC PHENOMENA.
the rays to pass, and its shadow was completely dark.
SUNSET.
On the Atlantic Ocean, near the coast of Portugal, we have noticed twilight in which the colors of the spectrum succeeded each other with great regularity, from bluish green to vivid red. These modifications are slow in our climate ; they permit us to enjoy fully the magic spectacle of those twilight scenes in which the sombre blue of the sea heightens the delicate hues of the sky. Near the equator, the duration of the phenomenon is much less, but it is generally extremely beauti- ful. M. Liais, a French astronomer of eminence, has thus described it in the narrative of his voy- age to Rio Janeiro :
" Almost immediately after the setting of the sun, a rosy tinge is seen in the east. Then there soon becomes visible above it a dark segment of sky, frequently of a greenish color. The rosy hue extends and broadens toward north and south, and, eleven minutes after its appearance in the east, begins to be seen in the west, the zenith remaining blue. In reality, a rosy coloring exists all aroTind the zenith, clear to the horizon, excepting at the east, where a grayish blue or greenish gray rests on the horizon, and at the west, where a white
SUNSET. 21
segment may be noticed. Eight minutes after its appearance in the west, the rosy coloring which had remained all the time at the west, but was gradually growing feebler, disappears altogether on that side. At the west can be distinguished a white segment, bordered with an arc of vivid rose- color, above which appears the deep azure with a splendor and intensity of tint impossible to describe. This arc descends, gradually, toward the horizon. It then becomes greatly flattened and assumes a vivid scarlet or orange red. It sets, at length, when the sun is 11° below the horizon.
" When the red arc is very low, and on the point of disappearing at the west, a second rosy coloring appears gradually and simultaneously at the west and the east, making a complete circuit of the zenith, which remains blue all the time. At the west, a space of silvery white separates the two rose-colored arcs. By degrees, as the sun de- scends, the second rosy coloring is seen to disap- pear first at the east, withdrawing toward the north and south without passing by the zenith. Then, at last, the first rose-colored arc sets, and there remains only the second arc, which is in the west, and has the form of a flattened arch, with a white segment below it. Finally, this second
22 METEOKS AND METEORIC PHENOMENA,
rose-colored arc, which assumes a still redder hue as it descends, sets when the sun is 18° below the horizon."
We will also quote the description of a sunset on the Desert of Sahara, as given by M. Charles Martins in the Revue des Deux Mondes, August 15, 1864 :
" Each sunset was a veritable feast for our eyes, and a delight as well as a source of astonishment for the mind, especially when the atmosphere was not completely serene. The coloring of the sky is then more vivid and more varied. Gradually, as the sun approaches the horizon, the gray dishev- elled clouds of the overarching sky — those latest emissaries of the northern mists and fogs — become fringed with purple tints that grow more and more intense, while the rounded contours of the white clouds reposing on the distant summits take on a yellow bordering, and seem to be set and chased in the rich gold that fills the western heavens. So soon as the sun has descended below the horizon, the softest ruddy tint spreads over the whole western sky. An emanation of the departed lu- minary, it colors all the mountains. One of these, visible from Biskra, is called DjebelrHaminar- Kreddou — the mountain with the rosy cheek. It deserves this name, because, long after the setting
SUNSET. 23
of the sun, it retains a rosy hue, like the blush of a young girl. Through the effect of contrast with the red, the blue of the sky assumes a watery- green tinge. Little by little the rose-color fades, the illuminated arc contracts, and the light that shines on it is as white and pure as that which should glow in the realms of space beyond the limits of our at- mosphere. Thanks to the transparency of the at- mosphere, all the outlines of terrestrial objects are clearly defined. The delicate edges of the leaves of the palm-tree become more visible than in the full light of day, and when the whole tree stands out against these backgrounds of alternate yel- low, red, and white, it seems as though the poetic beauty of this noble plant were revealed, for the first time, to the gaze. However, night comes on. The planets and then the grand constellations first appear ; the sky becomes peopled with myr- iads of stars. The upper vault grows brighter, and the milky way, which is but a dim, whitish belt, as seen in the higher latitudes, looks like a sparkling scarf of diamonds flung athwart the celestial dome. The moon is no longer that pal- lid star whose melancholy glance seems to sympa- thize with the dulness of our foggy regions ; it is a glowing disk of the purest silver, that reflects without weakening the rays that it receives, or is
24 METEORS AND METEORIC PHENOMENA.
a crescent rounded off to the full orb, by the ashy radiance which distinctly and sharply defines the entire outline. Such was the sunset of December 13, 1863, on the evening before our departure from Biskra ; it affected us deeply, for it was our adieu to our evenings on the desert."
THE TWILIGHT OF THE POLAR REGIONS. THE ANTI- TWILIGHT.
The rule generally admitted for the duration of the twilight is the descent of the sun 18° below the horizon. In many places, however, it lasts all night, at certain periods of the year? In the Scandinavian countries, in northern Germany, and even as low down as the latitude of Paris, this is the case about the period of the summer solstice.
When the upper regions of the atmosphere are filled with fine particles of ice, the darkness is not complete even when the sun is 30° below the horizon, as the long twilights of the polar regions sufficiently prove. In those gloomy countries there reigns, during the six months' night, a sort of half daylight, which is sometimes strong enough to read by, should the effulgence of the moon and the radiance of the aurora borealis aid the pale emanations of the sun.
'"
THE MIRAGE. 25
Yer y frequently one may notice, after the set- ting of the sun, when one is standing on an emi- nence, a red arch defined upon the eastern sky around a darkish-blue space. Under favorable circumstances, the line of separation is marked by a yellowish edging. This is the phenomenon that has been styled the anti-twilight. The apex, or culminating point of the arch, is directly opposite the sun, and attentive examination shows that the segment illuminated only by the scattered rays corresponds with the shadow of the earth pro- jected against the sky.
THE MIRAGE.
If in summer we look at objects visible across a field heated by the sun, they seem to waver and their shapes continually change. This effect is accounted for by the crossing and recrossing of thin streams of cold and warm air rising and de- scending. The luminous rays in passing through them modify their movements at nearly every in- stant.
The phenomenon known as the mirage, of which the most remarkable examples are met with in Egypt, have an analogous origin. In that country the atmosphere is usually calm and ex- tremely pure. At sunrise remote objects can be
26 METEOKS AND METEORIC PHENOMENA.
seen with the most perfect distinctness. From the borders of the Nile to the limits of the Des- ert, arise, from point to point, small eminences crowned with villages and groves of palm-trees, which look down upon each year's inundation of the river. Gradually, as the sun climbs above the horizon, the ground, becoming heated, imparts its superior temperature to the lower strata of the atmosphere. At such times, the undulating, tremulous motion of which we have spoken is fre- quently noticed. But when there is no wind, and the dead calm of the atmosphere allows the lower strata to expand without commingling with those that are resting upon them, the spectator might fancy that he had before him a huge lake, in the midst of which are seen the reversed images of the surrounding eminences and the villages that are built upon them. The magnificent blue sky seems to be reflected in it too; but, as one approaches, the imaginary sheet of water fades away, leaving only the burning sands in its place, while farther on the same deceptive picture is reproduced under a different aspect.
These appearances often misled the French troops in Egypt. Worn out with forced marches, dying of thirst under the scorching heat of an African sun, and choked by the clouds of sand that
THE MIRAGE. 27
filled the air, they would rush headlong toward the fancied water before them, but the delusive shore, alas ! always fled farther and farther at their approach.
To the distinguished savant Monge, who ac- companied the French expedition into Egypt, is due the elucidation of this phenomenon. He has demonstrated that the most rarefied strata of air, in this case, being the lowermost, a luminous ray darting from an elevated object toward the ground, deflects more and more in consequence of refraction, up to the moment when it is reflected from a last stratum, as it would be from a mirror, and then rises again, subject to a series of refrac- tions the reverse of those first encountered. It thus at last strikes the eye of the observer in the same direction as though it came from a point sit- uated below the level of the soil, presenting the reversed images as they would appear if he saw them on the surface of a placid lake.
Mariners frequently get a view of the mirage under circumstances the opposite of those that we have just set forth. The temperature of the sea, being colder than that of the superincumbent strata of air, renders them less dense below than above, and the reversed picture of distant shores or vessels is defined on the atmosphere itself.
28 METEORS AND METEORIC PHENOMENA.
Captain Scoresby made many such observations in the waters of Greenland.
" On the 19th of June, 1822," says this accom- plished navigator, in one of his narratives, " the sun was very warm, and the coast seemed suddenly to come from fifteen to twenty miles nearer. The highlands were raised so much to the view that we could see them as well from the deck of the ship as we could previously from the foretop. The ice on the horizon assumed the most singular forms ; huge blocks looked like pillars and columns ; the icebergs and field-ice resembled a chain of pris- matic rocks, and at many points the ice appeared to be in the air at a considerable height above the horizon. The ships that happened to be near us had the most fantastic aspect. On some of them the mainsail seemed to be reduced to a mere nothing, while the foresail looked several times as large as it really is.
" Above the vessels at a distance, we saw an ex- act picture of themselves, but reversed and mag- nified. In some cases this was at quite an eleva- tion above the ship, but then it was always smaller than the original. For some minutes we saw the image of a vessel that was really below the horizon, and one ship was surmounted by a picture of two like it, the one upright and the other reversed."
THE MIRAGE. 29
Among the numerous varieties of this phe- nomenon of the mirage, the one observed by Messrs. Soret and Jurine on the Lake of Geneva, which might be correctly styled the lateral or horizontal mirage, is hot the least curious. These gentlemen were at a window in the second story of a house close to the shore, and were looking with a spy-glass at a number of sail-boats passing from right to left, in the middle of the lake, while, nearer to the shore, the same fleet of boats ap- peared to be sailing in exactly the opposite direc- tion ! This was an illusion analogous to the Egyptian mirage, and explicable in the same way. Close to the shore the air had been in the shade a part of the morning, and was comparatively cool- er, while out in the open lake it had been heated by the blaze of the sun. Hence, vertical strata of air of different densities had remained motion- less, or nearly so, in the prevailing calm, and re- fraction had produced its magical effects from side to side, instead of above and below, as in the cases previously detailed.
When, instead of occurring in level and regu- lar strata, these effects of refraction and reflection take place in curved and irregular strata, a mi- rage is produced in which the images are distorted in every respect, broken or repeated over and over
30 METEORS AND METEORIC PHENOMENA.
again, and separated for considerable distances from each other. This is what takes place in the fantastic aerial vision formerly ascribed to the fairy Fata Morgana, and sometimes attracts multitudes to the sea-shore at Naples, and at Reggio on the Sicilian coast.
" For an extent of several miles along the coast of Sicily," says an eye-witness of this extraor- dinary spectacle, " I &aw the sea assume the ap- pearance of a chain of gloomy mountains, while the waters in the direction of Calabria remained perfectly smooth. Above them was seen, in chiaro-oscurOj a range of many thousand pillars, all of equal height, distance, and degrees of light and shade. In the twinkling of an eye, these pilasters lost half their height, and seemed to bend over and resolve themselves into arches and arcades like the old Eoman aqueducts. Then a cornice formed along the top, and an endless num- ber of castles, all alike, appeared. These pres- ently faded away into towers that vanished also, leaving nothing visible but a long colonnade, suc- ceeded in its turn by windows, and then by pines and cypresses also indefinitely repeated."
Sometimes these objects are depicted in the sky at a great height above the ground. On such occasions some of them are in rapid motion, while
THE MIRAGE. 31
others are at rest. Their outlines often gleam with rainbow colors, and, as the light augments, their form becomes more and more aerial, until they melt away and disappear when the sun shines forth in all his splendor.
Bernardin de Saint Pierre relates the follow- ing incidents : " A very singular phenomenon was once described to me by our celebrated paint- er, Yernet, who was my friend. During his youth, when in Italy, he devoted himself particularly to the study of the sky, a more interesting branch of his art, no doubt, than the study of the antique, since it is from the sources of light that the colors and aerial perspectives issue that form the charm of pictures as well as of Nature itself. Yernet, in order to fix their variations, had conceived the idea of painting on the leaves of a book all the shad- ings of each principal color, and then had marked them with different numbers. When he was de- signing a sky, after having sketched out his rough draft and the forms of the clouds, he would rapid- ly note down all the fugitive tints on his canvas with figures corresponding to those in his book, and then color them at his leisure. One day he was greatly astonished to see in the sky the ap- pearance of a city reversed. He could perfectly distinguish the steeples, the towers, and the
32 METEORS AND METEOKIC PHENOMENA.
houses. He hurriedly made a sketch of the phe- nomenon, and then, determined to know the cause of it, he set out, following the direction of the wind, into the mountains. But what was his surprise when, some twenty miles distant, he found the very city the spectre of which he had beheld in the sky, and had a sketch of in his portfolio ! "
It is perhaps to the effects of mirage that we must attribute the extraordinary faculty of sight once so famous on the lie de Frcmce. Toward the close of the last century, a colonist named Bottineau could make out vessels which were still a considerable distance below the horizon. The new science which he pretended to have con- structed, by combining the effects produced by dis- tant objects upon the water and upon the atmos- phere, he called Nauscopy. He went to Paris, provided with letters from the intendant and the governor of the island, attesting the reality of his discovery ; but he could not even succeed in ob- taining an audience with M. de Castries, who was then Minister of Marine. No one took the pains to investigate the means by which he mastered such surprising results. In the latter, Arago was not altogether an unbeliever, as we glean from his efforts to discover whether certain phenomena of the twilight, in which the shadows of distant
THE MIRAGE. 33
mountains probably play a part, would not help to clear up this important secret. The poor colonist returned to his home on the Isle of France, where he was afterward seen passing most of his time, until he died, on the sea-shore, his gaze fixed on the horizon, and continuing to excite the amaze- ment of all by the accuracy of his predictions.
CHAPTEE II.
CLOUDS AND FOGS.
The Clouds.— Formation of the Clonds and Mists.— Influence of the Ma- rine Currents. — Extraordinary Fogs. — Appearance and Motion of the Clouds.— Hail-Clouds.— Forms of the Clouds.— Cloud-Kings.— Influ- ence of the Mountains.— Distribution of the Clouds.— The Spectre of the Brocken.— The Shadow of Mont Blanc.
THE CLOUDS.
ARISTOPHANES, in his play of The Clouds, puts the following invocation into the mouth of Soc- rates :
" ' O sovereign master ! thou vast air that dost envelop all parts of the earth ! — luminous ether ! and ye, O venerable goddesses, the clouds, mothers of the thunder and the lightning ! — arise, O sover- eign clouds ! and appear on the empyrean heights. Come, O august clouds ! whether ye rest on the sacred summits of Olympus, white with snow ; or, in the plains of the Ocean, your father, ye form dances in honor of the nymphs ; whether at the mouths of the Mle ye dip up his waters in golden urns, or whether ye dwell on the Palus Mseotis,
FORMATION OF THE CLOUDS AND MISTS. 35
or upon the stormy rock of Mimas, hearken to my prayers, and receive with favor the sacrifice I make.'
" Chorus of Clouds. — 4 Eternal clouds, from the resounding bed of the Ocean, our father, let us rise, in light, transparent mists, to the woody summits of the lofty mountains, that we may look down into the distance upon the hilly country ; the sacred earth, prolific of fruits ; the courses of the rivers, and the sea whose billows dash and break roaring against the crags ! For the eye of the heavens blazes eternally with dazzling efful- gence. Let us scatter and dissolve these dull mists that enfold us, and show ourselves to the earth in our immortal beauty.' ':
The charm of this poetry lies in the truth as well as the beauty of its images ; but the brief meteorological sketch which Aristophanes then gives, according to the theories of his epoch, is an example of the errors that must follow observation when not based, as it is to-day, upon knowledge of the physical laws the influence of which we are about to describe.
FORMATION OF THE CLOUDS AND MISTS.
The formation of mists and clouds is due to the presence of watery vapor in an atmosphere
36 METEORS AND METEORIC PHENOMENA.
colder than the soil in which this vapor becomes visible, exactly like the steam that rises over boil- ing water.
The minute bodies of which the mist is com- posed are hollow globules, resembling soap-bub- bles, or droplets of water, the diameter of which, measured through the microscope, is smaller in summer than in winter. This diameter increases also when rain is threatened.
Fogs being generally the result of the cooling of the atmosphere, and of the mingling of two currents of air of unequal temperature charged with moisture, they are seen forming, especially at morning and evening, and chiefly during the au- tumnal season, over rivers and lakes, the water of which is then much warmer than the atmosphere.
The formation of vapor is most abundant when the air is the dampest. Kaemtz, in his " Course of Meteorology," cites an observation made by the ancients in reference to the volcano of Stromboli : " When this volcano is covered with a cloud, the inhabitants of the Lipari Islands know that it will soon rain : but this does not happen, as they suppose, because the volcano is more ac- tive just before a shower ; it is because the air, laden with watery vapor, cannot completely dis- solve that which escapes from the crater."
INFLUENCE OF THE MARINE CURRENTS. 37
Columns of mist ascend sometimes at certain points where the nature of the soil and vegetation give rise to a more active evaporation.
After heavy rains, and when the sun shines out again, these mists are seen appearing on the slopes of the mountains, where the ground is nearly always either arid or studded with woods, and following the undulations and accidents of the surface.
The same phenomenon occurs in Switzerland above lakes the temperature of which is more or less elevated, according to whether the streams that feed them do or do not issue from the region of eternal snow.
Mists form under circumstances also that are different only in appearance ; for instance, when there is a thaw, and the air, laden with humidity, mingles with the colder air that is in contact with the ice that still covers the waters. The same cause produces the summer fogs seen along rivers, especially after heavy storms of rain.
INFLUENCE OF THE MARINE CURRENTS.
Marine currents of elevated temperature, such as the Gulf Stream, occasion frequent fogs on the colder coasts against which they beat. The dense fogs of Newfoundland and of the British Islands
38 METEORS AND METEORIC PHENOMENA.
are ascribable to this influence, which has been noted in other regions — the Aleutian Isles, for instance, lying in the track of the great tepid current, analogous to the Gulf Stream, that crosses the North Pacific.
Lieutenant De Haven, of the United States Navy, during his expedition in search of Sir John Franklin, saw, at the northern extremity of Wellington Channel, a dense fog-bank motionless and suspended in the air — a water-sky, rising, to all appearance, above the Polar Sea, discovered in 1854 by Dr. Kane, the open waters of which are tempered by the submarine current found to ex- ist in Davis's Strait.
EXTRAORDINARY MISTS.
Mists are sometimes of remarkable extent and duration. In 1821 and 1822 mists of this kind occurred in England and France, so dense that people could gaze upon the sun at noonday with the naked eye. In 1783 a similar fog covered nearly all Europe for the lapse of a month.
We read in a " Journal of the Reign of Henry III.," published in the French language :
" On Sunday, the 24th of January, 1588, there rose over the city of Paris and its environs so dense a fog, lasting from noon until the next day, as
EXTRAORDINARY MISTS. 39
never was seen before within the memory of man. It was so black and thick that two persons walk- ing together in the streets could not see each other, and were compelled to provide themselves with torches, in order to recognize one another, when it was not yet three o'clock. Yery many wild geese, and other flying creatures of the air, were found where they had fallen bewildered in the court- yards of the houses, having dashed themselves against the buildings and the chimneys."
Captain Berg, a Russian officer, mentions a sort of mist that appears to rise from the sea in stormy weather, and is called smoke. We have repeatedly witnessed this phenomenon, which is ascribable partly to electricity. M. Peltier, the French savant, in one of his learned treatises, divides mists into two classes, viz., the electric and the non-electric. He explains the condition of the former by the combined influences of the earth and the higher regions of the atmosphere. More- over, it has been ascertained that the electric fluid is constantly developed in the atmosphere sur- rounding cascades, where the water is incessantly reduced to fine spray, and this remarkable phe- nomenon might lead to a better determination of the influence, no longer to be denied, of atmospheric electricity on the formation of aqueous meteors.
40 METEORS AND METEORIC PHENOMENA.
Luminous mists are not uncommon. Mr. Wartmaim, of Geneva, in a letter to M. Elie de Beaumont, given in the Comptes Rendus of the Academy of Sciences of Paris, for December 25, 1859, has described one of these strange meteors, which continued to appear for nine successive nights, viz., from the 18th to the 26th of Novem- ber, 1859. The new moon, which was below the horizon, could not contribute to this phenomenon. The mist, which was very opaque, was still not rnoist enough to dampen the ground. It threw off light enough to enable one to distinguish the smaller articles in a room where the observer stood. A person who was proceeding on foot from Geneva to Annemasse, in Savoy, on the 22d of November, stated that he could see the road during the night as well as he could have done by the light of the moon.
Phosphorescent mists of the luminous order are usually dry mists, like those of 1783 and 1831, to which we shall refer again when we come to igneous meteors.
Certain mists that form over marshy plains have a peculiar odor, occasioned probably by the miasma which they contain and bear along with them.
In regions where it seldom rains, as for instance
APPEARANCE AND MOTION OF THE CLOUDS. 41
at Lima and around it, the mists caused by local circumstances last sometimes for a part of the year, serving to moisten the soil and maintain the fresh- ness of the vegetation.
Mists are often seen forming over hollows where the water is nearly always colder than the air, and determines the collection of vapor above it. Humboldt states that in the South Sea Islands the shape of these mists frequently reproduces that of the hollows exactly.
APPEARANCE AND MOTION OF THE CLOUDS.
The appearance and movements of the clouds, the formation of which is due to the same causes that produce the mists, are to be numbered among the chief indications that announce to us the changes brought about in the aerial ocean by the variations of electric tension, temperature, and humidity.
Mountain-summits are often enveloped in clouds produced by the damp air, and by the watery vapor that condenses by degrees as it rises toward those colder regions. These clouds are very frequently observed to disperse, as they get farther away from the mountain-tops and encoun- ter air-currents of a more elevated temperature.
" Often," says Kaemtz, " dark clouds pass rap-
42 METEORS AND METEOEIC PHENOMENA.
idly over the Hospice of Saint Gothard and pre- cipitate themselves in heavy masses into the Val Tremola. One would think, to look at them, that all Lombardy was about to be buried under a dense fog ; but, at the outlet of the Yal Tremola, it is already dispersed by the warm currents of air ascending."
During very violent winds, clouds are seen, in consequence of like circumstances, clinging to the peaks of mountain-ridges, and apparently motion- less, while around those peaks the intervals re- main perfectly clear.
The appearance of remarkable clouds suspend- ed on the summits of lofty mountains sometimes announces tempests, always preceded by atmos- pheric variations, which practice in observing natural signs teaches us to recognize. Thus, the people of the Cape of Good Hope prognosti- cate tempests from the southwest (so formidable in their latitudes) whenever they see a compact, lead-colored cloud gathering around the summits of their highlands, and particularly on Table Mountain.
ICE-CLOUDS.
The mists that form on the surface of the ground, either in the depths of valleys or on the
ICE-CLOUDS. 43
heights, become clouds whenever, carried upward by ascending currents, they remain suspended in the atmosphere above us. Clouds are also formed directly in the air by the meeting of two winds laden with moisture and of unequal temperature, or by the condensation of copious vapors which rise toward the colder regions of the atmosphere.
Sometimes there are several beds of cloud resting one above the other, and, generally, the whiter they look, the higher they are.
The temperature of the regions that the clouds ascend to is often several degrees below zero, and, as may readily be understood, they are then com- posed of icy particles, like the fine needles of the mists that ascend in fleecy masses during severe cold weather, and are often seen glistening in the sunlight.
In reference to this subject we shall cite an important observation that concerns meteorology in the highest degree. It was enunciated in a re- markable lecture on " the influence exerted upon vegetation by the atmosphere."
The lecture in question was delivered by one of the most learned and courageous scientific ex- perimentalists of France, Professor J. A. Barral, before the Chemical Society of Paris.
" On July 25, 1850, my friend M. Bixio and
44 METEORS AND METEOKIC PHENOMENA.
I were fortunate enough to ascend in a balloon beyond the stratum attained by Gay-Lussac in 1804, and some surprise was manifested that we, in the midst of a violently-agitated atmosphere^ and in the bosom of a vast ice-cloud, should have found 39°. 7 (by the aid of numerous and delicate instruments graduated by M. Regnault), or, in other words, the temperature at which mercury solidifies, in the same region where Gay-Lussac had noted only 9°. 5, when the air was calm and the sky clear. This surprise had no other basis than a defective interpretation of the facts already established. At the present day we have to ad- mit that, even in the very highest regions of the atmosphere that men have reached, there are con- siderable variations in the temperature of the air as well as upon the surface of the earth. A cir- cumstance no less remarkable is, that, in mid- summer, clouds of more than four thousand yards in thickness, composed of numberless little needles of ice, may be seen gliding above our heads at a velocity of at least thirty miles an hour. In those regions where eternal silence reigns, and where all life has ceased, are condensed, along with the last watery molecules that have mounted from the bosom of the earth and the clouds, those innumerable exhalations which we are wont to
ICE-CLOUDS. 45
term the impurities of the atmosphere. The mat- ter contained in them descends again with the rain, the hail, and the snow, to the surface of our planet, where it is disseminated, and conveys to the barrenest rock the elements necessary to support vegetation, which may thus develop and distribute themselves in nearly every latitude, whatever may be the character of the soil that receives the fertilizing shower. The lower aerial strata that touch the surface of the solid crust of our globe, and the doubly extensive surface of its seas and oceans, after having become laden with various materials, dilate by the effect of heat, and then ascend until they meet the chill that con- denses them in the higher regions, and causes them to fall again to the surface. Thus a contin- ual rising and falling motion is produced in that atmospheric belt, between four and five miles in thickness, which we have been able to sound. The rain and the snow are formed, and, borne far away from the spot which saw the birth of the embryo cloud, they go forth to fertilize distant plains by besprinkling them with water that is saturated with a new air."
In England the latest winter ascensions of a learned aeronaut, Mr. Glaisher, enabled him to
detect, at an elevation where the temperature was 3
46 METEORS AND METEORIC PHENOMENA.
very low during the summer ascensions, a current of warm air, seven hundred yards in thickness, charged with vapor. The latter soon afterward descended upon the city of London and enveloped it in a dense fog.
These interesting observations go to prove that the loftier regions of the atmosphere are traversed, like the depths of the ocean, by great currents of unequal temperature, which, no doubt, contribute to the maintenance of a general system of aerial circulation, and which, sometimes descending to the surface of the earth, there produce those great changes of temperature that meteorological obser- vation will one day, perhaps, enable us to foresee with sufficient accuracy.
THE FORMS OF THE CLOUDS.
The causes which determine the forms, the color, and the elevation of the clouds, are not yet known. The double action of the currents of warm air which ascend from the earth in the day- time and the horizontal currents, suffices to ex- plain the suspension in the atmosphere of the vis- ible vapors, heavier as the latter are than the medium in which they float. According to Presnel, the solar heat absorbed by the clouds makes a sort of balloon of them, which rises the
THE FORMS OF THE CLOUDS. 47
higher according to the greater elevation of the temperature. It is owing to these influences that clouds are generally higher at noon than toward evening.
M. Jamin, in his course of lectures at the Sorbonne, has demonstrated that the aqueous particles whose aggregation makes a cloud, are in the condition of full droplets, and that, when the radius of these droplets is sufficiently small, but little effort is required to sustain them at certain heights. This effort is always supplied by the continual displacements going on in the atmos- phere.
Dr. Howard, a learned English writer on phys- ical and meteorological science, was the first who distinguished in the clouds the four leading forms of Cirrus, Stratus, Nimbus, and Cumulus. He classifies them in his " Essay on the Modifications of Clouds, and on the Principles of their Produc- tion, Suspension, and Destruction," published at London in 1802.
The cirrus consists of thin, transparent clouds, which look like delicate plumes, and are always seen at a great height. They are sometimes ob- served in parallel bands, or in filaments, stretching north and south, appearing to diverge from one point on the horizon and to converge toward an-
48
METEORS AND METEORIC PHENOMENA.
other diametrically opposite. " Many meteorolo- gists," says M. Charles Martins, "for instance,
FORMS OF THE CLOUDS — THE CIRRUS, OB CAT-TAILS.
Howard, Forster, Peltier, and others, think that the cirri serve as conductors between two distant
centres of electricity of different poles, in which the fluid is seeking an equilibrium, and that the
THE FORMS OF THE CLOUDS. 49
flexibility of the clouds at length gives them the rectilinear form required by the necessity for the shortest possible transit from one focus to the other. The whiteness of the cirri arises from the icy particles and snow-flakes of which they are composed. Their peculiar appearance has earned for them the various titles of " cat-tails"
50 METEORS AND METEORIC PHENOMENA.
" horse-tails" " mackerel-sky" etc. They nearly always portend a change of weather.
The stratus is the long horizontal belt of smoke-colored clouds that often extends across the horizon at sunset, and that may be seen forming, on fine summer evenings, above expanses of water and damp meadows. These cloudy bands may be thick and extensive enough to cover the sky, but they never yield rain.
The nimbus is a mass of dense, black clouds, with jagged borders, which announce rain o'r storm. Hence a cloud of any kind resolving it- self into rain always takes the form of the nim- bus.
The cumulus consists of what we may term "the fine -weather clouds." Their whiteness, which contrasts with the blue of the sky ; their rounded, half-spherical forms ; their well-defined outlines, make it easy to distinguish them. Piled up on the horizon, they frequently assume the shape of lofty snow-clad mountains, and when they are seen to darken at the same time that the lower bed of the cloud spreads out into a stratus, rain may be expected.
The great poet Goethe, who was also a distin- guished naturalist, has left us some remarkable points relating to meteorology. We will quote a
THE FORMS OF THE CLOUDS. 51
passage from one of his learned essays on the sub- ject, as epitomized by the French scwant Mar- tins, who has edited the great German's scientific lucubrations on natural history :
"When Goethe was made acquainted with Howard's theory, he hastened to verify its princi- ples, and to that end undertook a series of experi- ments and observations. These observations were chiefly made during the course of a journey in Bohemia, between the 23d of April, 1820, and the 28th of May in the same year. They were ac- companied by considerations of a general charac- ter, to which we would, for a moment, call atten- tion.
" Goethe, in common with many other mete- orologists, distinguishes three regions in the atmos- phere : the most elevated is characterized by its dryness; it therefore tends to absorb the moist- ure of the lower strata; and in this region the sky is clear, or covered with a few clouds disposed in the cirrus form. Goethe did not remark that, in the icy heights of the atmosphere, the vapors become converted into snow, and that the cirrus is made up of masses of snow-flakes. In the in- termediate regions we find the cumulus, whose strange and ever-varying forms have become the object of many superstitious notions among the
52 METEOES AND METEOEIC PHENOMENA.
dwellers in mountainous districts. Below the cirrus and the cumulus extends the stratus, which occupies the lowest part of the upper atmosphere. " The higher and the lower regions are in a state of perpetual conflict. Sometimes the upper regions prevail, and the cumuli, being rent asunder, rise and are scattered abroad in the form of fleecy particles. Sometimes, on the other hand, the lower region is the more powerful ; then, the cumulus is lengthened out to a stratus, and the heaped-up mass of clouds becomes a nimbus big with rain. The formation of clouds may take an opposite course : dense fogs ascend from the earth in the shape of elongated strata, and group them- selves into thick cumuli, or separate and form the cirrus. Goethe holds persistently to this conflict between the higher and lower regions of the at- mosphere, and claims to have noticed that the east and north winds cooperate with the action of the upper regions, and those of the west and south with the action of the lower layers."
DISTRIBUTION OP THE CLOUDS. THE CLOUD-EING.
The distribution of the clouds in different parts of the globe has been too imperfectly ob- served to enable us to deduce any general laws therefrom. Moreover, this distribution is evi-
THE CLOUD-RING. 53
dently in direct relation to the quantity of rain that falls in each region, and we shall presently sum up the data thus far obtained in reference to that branch of meteorology which relates directly to cultivation and to the fertility of the soil.
This fertility is not due merely to the benefi- cent action of the rain that waters our fields, nor to the snow that protects them in winter. The clouds, in spreading their mantle over the earth, keep in its heat or prevent excessive drought, and, as Maury has well said, in his "Physical Geography and Meteorology of the Sea, " " when their task is accomplished at one point, the winds bear them away, to perform the same regulating function elsewhere."
In the zone of the equatorial calms one can best appreciate this influence of the clouds upon climate and vegetation. "While in the re- gion of the trade-winds, both north and south of the equator, the sky is usually clear or dotted with light clouds ; we, on the cootrary, when ap- proaching the zone of calms, see the sky become obscured and covered with dense vapors, arising from the masses of air saturated with moisture which the trade- winds continually sweep into that zone. The dais or disk of clouds thus formed extends around the globe like a ring, or belt, which
54 METEORS AND METEORIC PHENOMENA.
is carried from the north to the south, or from the south to the north, within certain limits, accord- ing to the season, alternately protecting the dif- ferent parallels that it covers from the blaze of the sun, and bringing them rain at given periods.
INFLUENCE OF MOUNTAINS. THE SPECTRE OF THE
BROCKEN.
We have already referred to the influence ex- erted by mountains on the condensation of vapors. M. de Gasparin, in his "Rural Meteorology," cites quite a remarkable observation in connection with this subject. " It is known," says he," that the narrow passage leading into the harbor of Plymouth is bounded on the east and west by two promontories covered with woods. J. Har- vey has noticed that a dense and quite compact cloud, coming from the west, disappeared in pass- ing over the strait and formed again upon reach- ing the opposite point of land."
The abundance of clouds in mountainous countries, their capricious forms, and frequently strange distortions, have furnished geniuses and poets with beautiful similes. Popular traditions show us that these natural phenomena have long been the source of superstitions that have not yet entirely died out. Thus, in certain parts of the
THE SPECTRE OF THE BROCKEN. 55
"V osges Mountains, the long, black trains of clouds that unroll and wind fiercely down through the deep gorges, at the approach of storms, still in- spire terror, as a token of the presence of evil spirits sweeping by with the tempest.
A wonderful phenomenon, the Spectre of the Brocken, was long explained by a superstitious peasantry as the work of direct supernatural in- tervention. One of the best descriptions of this phenomenon was given by Mr. Hane, who wit- nessed it on May 25, 1797 : " After having scaled the summit of the mountain more than thirty times, in vain, at last he had the good fortune to see the object of his curiosity. The sun rose at about four o'clock in the morning, and the weather was fine. The wind was driving before it toward the west masses of transparent vapor, which had not yet had time to condense into clouds. About a quarter-past four, the traveller saw, in the di- rection of Achtermannshohe, a human figure of enormous dimensions. A gust of wind having nearly blown away Mr. Hane's hat, he quickly put up his hand to retain it, and the strange fig- ure made the same gesture. Mr. Hane then im- mediately made another motion, stooping down- ward, and this act was likewise reproduced by the spectre. Another person joined Mr. Hane, at
56 METEORS AND METEORIC PHENOMENA.
this moment, and the two gentlemen, placing themself together on the very spot from which the apparition had been noticed, looked toward Achtermannshohe, but saw nothing. However, a little while afterward, two colossal figures ap- peared in the same direction imitating the motions and gestures of the two observers, and then dis- appeared. They showed themselves again, a little later, accompanied by a third figure. Sometimes these shapes were feeble and indistinct ; at others they were very intensely marked and their out- lines sharply defined. The reader will have guessed that the phenomenon was produced by the shadow of the spectators projected on a cloud. The third figure was undoubtedly due to a third person half hidden behind some broken mass of rock."
During his journey with La Condamine among the Cordilleras, Bouguer, a member of the French Academy of Sciences, sent out with the former to South America to measure a degree of the earth's surface, witnessed a phenomenon, similar to the one just described, from the sum- mit of Pambamarca :
" What astonished us," says he, " was that the head of the shadow was adorned with a halo formed of three or four small concentric crowns
THE SPECTRE OF THE BEOCKEN. 57
of very vivid color, each one with the same vari- ety as the first rainbow, the red on the outside. This made a sort of apotheosis for each spectator, and I must not forget to add that each of them tranquilly enjoyed the pleasure of seeing him- self decorated with all these crowns, without even catching a glimpse of those of his neighbors."
Kaemtz has verified the same thing on the Alps. So soon as the shadow was projected on a cloud, the head was seen surrounded by a lumi- nous halo. Scoresby in the polar regions, Ramond in the Pyrenees, and De Saussure, have all seen and described this curious phenomenon, which is known under the name of Anthelia.
Sometimes it is observed under more ordinary circumstances, at the rising and the setting of the sun, when fogs are resting on the ground. Fre- quently the aerial figure, the head of which is al- most always surrounded with luminous rays, is no larger than life. It may be readily conceived that such apparitions gave rise to the quaint le- gends heard in different countries, particularly in mountainous regions where the lofty summits, crowned with clouds of varying outline and ever- changing colors, have played so grand a part in the composition of religions fables.
When the sun is just at the horizon, one may,
58 METEORS AND METEORIC PHENOMENA.
if standing close to a railway, see the shadows of the telegraph-posts appear on the long pennant of white steam that rises from the locomotive, and floats over the train. Aeronauts often see the magnified image of their balloon upon the clouds, in the elevated regions through which they pass. The phenomenon is in every case of the same gen- eral nature as the famous Spectre of the Brocken.
THE SHADOW OF MONT BLANC.
When the spectator happens to be standing on the summit of a very high mountain, the shadow projected by the setting sun is directed upward to the sky, and sometimes produces a magnificent phenomenon, which was observed by Messrs. Bravais and Martins in one of their scientific excursions to Mont Blanc. M. Bravais has given the following description of it :
" As the sun was approaching the moment of his setting, we looked in the direction opposite to the luminary, and beheld, not without some sur- prise, the shadow of Mont Blanc defined upon the snow-clad mountains in the eastern part of the panorama before us. It gradually rose in the at- mosphere until it attained the height of an entire degree, remaining all the while distinctly visible.
" The air above the apex of the shadow was
THE SHADOW OF MONT BLANC. 59
tinged with that purply rose-color, which one sees, in fine sunsets, suffusing the loftiest peaks. The edge of this color presented a zone of deeper in- tensity, and that continuous bordering enhanced the splendor of the phenomenon.
" Let any one imagine the mountains in the great valley of Aosta projecting their shadows at one and the same moment upon the atmosphere, the lower part dark with a slight greenish tinge, and, above each of these shadows, a breadth of purply rose-color, with a belt of deep rosy-red sep- arating it from them ; let him add to that the sharp uprightness of the cones and peaks in the shadow, especially of their uppermost ridges, and, finally, the effects of perspective, making all these lines converge one upon the other toward the very summit of the shadow of Mont Blanc, that is to say, toward that point in the sky where the shadows of our bodies should be. Even then he will have but an incomplete idea of the richness of the meteorological phenomenon that developed itself before us for some moments. It seemed as though an invisible being were in a throne girt round with fire, and that, on their knees, angels with glittering wings were worshipping him, all bending their forms toward him. At the sight of a spectacle so magnificent our arms and those of
60 METEOES AND METEORIC PHENOMENA.
our guides dropped motionless, and cries of enthu- siasm escaped our lips. I have seen the superb aurora borealis of the north, with its crowns in the zenith, and its variegated wavering colon- nades of pillars, far surpassing the finest devices of our pyrotechnists, but the spectacle presented by the shadow of Mont Blanc, in my opinion, went beyond them all."
CHAPTEE III.
RAIN, SNOW, AND HAIL.
Dew.— White Frost.— The Distribution of Rain on the Surface of tho Globe.— The Great Rains of India.— Regions without Rain.— Influ- ence of Forests.— The Softening of Climates — Forms of the Snow.— Flowers under the Snow.— Glaciers and Rivers.— Hail.
DEW AND WHITE FROST.
DEW — the bright deposit of limpid little drops which glisten in the morning light on the foliage, like pearls and diamonds — is caused by the con- densation of atmospheric vapor on substances suf- ficiently cooled during the night by radiation, or the loss of heat through the air. Doctor "Wells, an English physician, was the first to give this ex- planation, after a great number of experiments.
A lock of very dry wool weighing 10 grains, placed upon a plank sustained by four uprights, increased its weight only two grains by moisture, while a similar lock placed above it gained 14 grains, and another, laid on the grass, increased
62 METEORS AND METEORIC PHENOMENA.
16 grains. Thermometers substituted for these locks of wool exhibited the lowest range where the dew fell the most copiously. On the other hand, substances that do not so readily part with their caloric, such as the metals, remained dry, while others of greater radiating power lying close be- side them were covered with dew. A clear sky was found to be favorable to the cooling process, and consequently to the deposit of dew ; and the passing of a cloud, which gives heat for heat, was sufficient to arrest the phenomenon. Moreover, it was observed that less dew formed in the depth of valleys than on the tops of hills, from which a greater extent of clear sky could be perceived.
When the nocturnal radiation causes the tem- perature of a body to descend below zero, the watery vapor condenses into ice, and white frost is deposited instead of dew. A custom prevalent in India may serve to give an idea of the power oi this cooling process. Ice is habitually procured there by exposing shallow pails, filled with water, and isolated from the terrestrial heat by layers of loose straw laid beneath them, in some open place, during very clear nights. Under these conditions the temperature of water has been known to fall IT degrees.
In order to protect plants from the disastrous
DISTRIBUTION OF BAIN ON THE GLOBE. 63
effects of these frosts, it suffices to arrange a hor- izontal screen about two yards above the ground, to prevent radiation. In the open field, during the clear nights of the end of April and the beginning of May, the cold often destroys the buds of plants. This occurs when the moon shines in an uncloud- ed sky, but, should the latter be obscured, no such bad effects are observed.
The russet or " red moon " is thus explained : The luminary of night is often most wrongfully blamed by country-people, since it is really the serenity of the sky which is the cause of the hurt- ful chill, and the consequent loss of crops.
THE DISTRIBUTION OF RAIN ON THE GLOBED SURFACE.
The refreshing stimulus extended to plants by fogs and dew is but temporary. A humidity much more abundant is required by them. Al- though there are very heavy dews in Egypt, the vegetation of that country would soon disappear were it not that the inundations of the Nile make up for the extreme rarity of rain. In years when the overflow is but limited, those districts which it does not touch remain sterile. Farmers every- where, whether fearing an excess of moisture or of drought, attach great importance to the rain,
64 METEORS AND METEORIC PHENOMENA.
its quantity and its distribution throughout the seasons of the year.
Rain falls sometimes when no cloud is visible, and the sky is perfectly clear. Yarious observa- tions of this nature are cited by Humboldt and Arago. " The night was fine," says a savant of Geneva, " and the stars were shining with their ordinary brightness, when a rain composed of large, tepid drops fell over the city for six min- utes." The same phenomenon is reported by an eye-witness to have taken place at Constantine at noon, and with the sky magnificently blue and clear.
But usually it is after having passed through the cloudy form that the moisture of the atmos- phere precipitates itself, and the indications con- tained in the preceding chapter give the first ele- ments of the geographical distribution of rain.
To commence with, we have the equatorial zone, enveloped in its girdle of clouds, formed not only by the vapors arising from the warm waters of the ocean carried up by powerful ascending currents, but also by those that the trade- winds sweep thither from north and south. This is a region where rain falls every day and in great abundance, the mixture of the masses of saturated air with the cold atmospheric layers taking place
DISTRIBUTION OF BAIN ON THE GLOBE. 65
continually under a very hot sun. Mention has been made of calms sufficiently prolonged and ac- companied by rains heavy enough to make the water fresh on the surface of the sea. The mar- iner is shy of these latitudes, where the tepid and heavy atmosphere causes an irresistible languor and develops dangerous diseases. Storms are so frequent there thai; it is rarely one does not hear the thunder rumbling above the dense clouds with an echo like the fiercest electric explosions among mountains. The familiar expression Hacking-pot, so often on the lips of sailors, very appropriately conveys the effect of the sombre belt thus de- scribed after the unvarying blue of the trade- wind skies.
All the vapor disengaged in this immense equatorial boiler does not fall in rain at the same place. Atmospheric currents higher up than the trade- winds carry it toward the two poles. They come in contact with the surface of the earth in a region the limits of which vary with the annual advance of the sun, like those of the equatorial belt of clouds, and which, as a general thing, is fixed in the tropics. Places situated in this region have periodical rainy seasons called win- terings.
In our temperate latitudes, the commingling
66 METEORS AND METEORIC PHENOMENA.
of layers which produces the rain ceases to be the result of ascending currents meeting with the upper cold air. It is produced by horizontal cur- rents, the direction of which is generally opposite to each other. This rain falls at all periods of the year.
At the 60th degree of latitude we reach the circumpolar zone, where no rain falls in winter, owing to the extreme rarefaction of the limpid atmosphere, which extends over the immense ex- panse of snow, and no fogs are seen to form, ex- cepting in those regions where the water is open.
If we compare the system of the circulation of the waters upon the surface of the globe to an alembic with the fire at the equator, we shall see that the regions outside of the tropics perform the part of condensers. Lieutenant Maury has very strikingly illustrated the functions of this admira- ble apparatus. " The average amount of rain that falls annually upon the surface of our globe," he says, " has been estimated at 1.5 yards in depth ; Thus, then, to raise enough of water from the ocean, every year, in the form of vapor, to cover the earth with a spherical coating 1.5 yards deep ; to carry that watery vapor from one zone to another, and then to precipitate it in different forms at certain determinate points at chosen
THE GREAT BAINS OF INDIA. 67
epochs, and in appropriate quantities, such are the functions of the great atmospheric machine. The water vaporized in this manner being taken principally from the torrid zone, the atmosphere in that zone alone must absorb a liquid mass of nearly 5 yards in thickness, and 3,000 marine miles in breadth, upon a development of 24,000 miles ; raise it as high as the clouds, and then let it fall again upon the earth. This it must, moreover, do every year ! What a wondrous and powerful mechanism, then, is this atmosphere of ours, and how harmoniously its different elements must be combined in order that this work, which over- whelms the imagination, may be carried on with- out the slightest disarrangement ever manifesting itself in a totality of functions as complex as they are varied ! "
THE GREAT RAINS OF INDIA.
The regions where the monsoons prevail have an exceptional pluvial arrangement. In the month of April, the season of the northeast trade-winds closes in India. The vast deserts of Central Asia, heated by the sun, give a sort of breathing aspira- tion that produces the southwest monsoons. La- den with the vapors of the ocean and of the Ara- bian Gulf, these winds strike the Ghaut range of
68 METEOES AND METEORIC PHENOMENA.
mountains at right . angles, and there deposit an extraordinary quantity of rain, which Johnson tells us has been known to attain the enormous meas- urement of 14i inches in a single day. They then diverge toward the Himalayas, where the temperature is lower than on the summits of the Ghauts. There they abandon in the form of snow and rain nearly all the moisture with which they were charged, and thus it happens that, when they reach the arid wastes beyond those mountains, they rarely have enough vapor left to form clouds. It is at Cherrapondschi, among the Himalayas, that the maximum of rain-fall, viz., 17" yards per annum, has been found for the entire globe.
Owing to these rains, vegetation attains a prodigious development in India ; but they are accompanied by all sorts of pests, as Mr. D. War- ren graphically describes them in his work on British India.
"A suffocating calm," he says, "which pre- vails particularly about the end of the great heats, precedes the setting in of the southern mon- soon. With the end of May come on the first storms, which are brief, but of extreme violence. Thunder is heard in the distance at intervals ; the sun sets in a bed of clouds, and every evening the lightnings illuminate all points of the horizon.
THE GREAT RAINS OF INDIA. 69
The rain falls, for half an hour, in torrents ; after a few days it lasts longer, and toward the middle of June it rules the entire day, for, when it is not actually raining, the sky is at least covered with a dense and threatening curtain of clouds. It rains sometimes, particularly in July, for thirty or forty hours consecutively, and then not in fine lines, broken and almost imperceptible, as in our climates, but in straight, parallel streaks, and frequently like a sheet of water coming down all at once with the fury and impetuosity of a cas- cade.
" The miserable clay-huts of the natives become thoroughly soaked under this continual avalanche ; their roofs fall in and bury them, or, at all events, escaping that easier fate, they find themselves ex- posed to all the rigors of the open air, and perish in great numbers. This is the period of wide- spread distress, which does not spare even the nabob and the conqueror ; and the very reptiles, those of the most hateful species, like the rest, in- undated in their holes, dart to the surface of the soil and seek an asylum among the dwellings of men. Numerous varieties of snakes, centipedes, and . scorpions, climb your stairs, invade your houses, and glide into every room. It is impossi- ble to take a step in one's bedchamber at night
70 METEORS AND METEORIC PHENOMENA.
without a light, unless one is prepared to run the risk of a sting that may prove fatal. The utmost distrust must be felt of every thing that one touch- es ; a cruel bite may kill you from the inside of a boot or a sleeve. For some time you lead a life of continual alarm and disgusting contacts; but these annoyances are not of long duration. The monsoon begins to decline in the month of Au- gust, and dies away in the first days of Septem- ber. The five months that follow, until the be- ginning of February, are delicious, and make one forget those that went before ; there is rapture in the mere fact of existence, the air is so fresh and the face of Nature so lovely."
KEaiONS WITHOUT RAIN.
There are parts of the globe's surface where rain is almost unknown. Such are the coasts of Peru, and it is easy to discover the reason. They lie within the sweep of the southeast trade- winds. The latter traverse the Atlantic and there become laden with vapors, which they then deposit on their trip across the American Conti- nent, where the rain feeds the sources of the Rio de la Plata and the southern affluents of. the Amazon. Then, they pass on to the snowy peaks of the Cordilleras, where the low tempera-
REGIONS WITHOUT EAIN. 71
ture completely divests them of tlie moisture they may still have retained. We need not be sur- prised, then, that they are dry and cold when they sweep down the western slope of the Andes, and remain so until they meet the waters of the Pacific Ocean.
A large part of Australia also is in the track of the southeast trade-winds, and should have large rivers, like that intertropical portion of South America just mentioned ; but the contrary is the case. Maury explains this difference by the relations that exist between the direction of the winds and that of the coasts. " In Aus- tralia," he says, "the eastern coast runs in the direction of the trade-winds, while in South America it is perpendicular to that line. Conse- quently, in Australia, these winds only fringe the coast, so to speak, with their vapors, and dis- pense their rains over these parched lands so sparingly, that the trees, in order to retain the small amount of moisture allotted to them, are obliged to arrange their leaves in the same line as the rays of the sun, since, if they were in the natural position, they would be too quickly dried up. On the contrary, in South America, where the winds blow in a direction perpendicular to the shore, and cause the humidity with which
72 METEORS AND METEORIC PHENOMENA.
they are charged to penetrate to the heart of the country, one sees the leaves striving, as it were, to reach the sun's rays and present themselves to them in their fullest development."
The Desert of Sahara, situated in the domain of the trade-winds that cross the land only, is de- nied rain entirely, and shows us what our globe would be without the magnificent reservoir of the ocean. From the immense sandy plains of Africa there rises only a column of burning air, while not even a drop of dew falls to moisten the parched surface and there develop vegetation.
THE INFLUENCE OF FOKESTS.
The influence of forests, in reference to rain, has been established by numerous observations. Columbus mentions it in his "Journal of the Yoyage to America," where he attributes to the density and extent of the forests that covered the mountain-sides the abundance of rain to which he was so long exposed while coasting along the shores of Jamaica. He remarks that "formerly rain was no less abundant at Madeira and on the Canaries and Azores, but since the trees that gave shade have been cut down, it has become much less frequent in those countries."
Humboldt demonstrates that there exists a
THE INFLUENCE OF FORESTS. 73
frigorific radiation above wooded regions, that must condense the vapors. The summits of mountains covered with forests become enveloped with mists oftener than those of mountains that are bare, and springs of water are more frequent- ly found among them. Numerous plantations of trees in Egypt have caused the rains that had totally ceased to reappear — a fact that deserves especial mention. In some parts of the Antilles the clearing of portions of the soil has diminished the quantity of rain, and the watercourses have lost their abundance.
At Porto Rico a different plan has been pur- sued. A decree of the King of Spain prescribed that, every time a tree should be cut down, three should be planted for it, and the country has con- sequently retained its high fertility. The beauty of the soil and the abundance of water have left the land more productive than on the adjacent islands.
We extract from the scientific work of M. Boussingault a passage confirming the existence of similar relations between the clearing away of the woods and the quantity of water: "In the valley of Cauca," he says, " it is well known that such and such a district, whose soil and me- dium temperature are favorable to the cultivation
74: METEOES AND METEOEIC PHENOMENA.
of the cacao-tree, still gives no good result if the latter be placed too near to the forest. But, when these forest-lands are cleared, and transformed to fields of yucca, sugar-cane, and maize, the cacao- tree flourishes remarkably. The following fact was obtained from Don Sebastian Marisansena, a resident of Cartago. Haying procured the title of capitan poblador to found a village at La Balsd, at the foot of the Quindin range, he began by putting in a plantation of cocoa-trees. Dur- ing the first ten years the crops amounted to little or nothing, because the rains were too fre- quent. The hacienda, or farm, began to be pro- ductive only when the inhabitants of La Balsd were numerous enough to make the clearings ex- tensive. Then at length the sun could ripen the cacao. In 1816, political events led to a large emigration of the people, only the negroes re- maining on the farm. Six years later, the sur- rounding fields were again transformed to forests ; the crops diminished more and more, and in 1827, when I passed through La Balsd, they had not gathered any cacao for three years."
AMELIOEATION OF CLIMATE.
The clouds when they dissolve in rain restore to the atmosphere all the heat that was taken up
AMELIORATION OF CLIMATE. 75
in forming them. Every one may have observed the increased mildness of the atmosphere after a shower of some duration. This circumstance powerfully affects the climates of the higher lati- tudes, especially in the southern hemisphere, where the counter trade-winds of the northwest con- dense their abundant vapors. It has been ob- served that, relatively to their position, the south- ern Shetlands have no very cold winters ; a fact undoubtedly due to the great quantity of heat disengaged during the rains.
The quantity of rain that falls on the western slope of the Patagonian Andes (and, according to Admiral Fitzroy,. it amounts to more than four yards in forty days) imparts a remarkable degree of heat to the winds that descend upon the other slope. It is to them, as well as to a feeble oce- anic current, that the extraordinary climate of the Falkland Islands is to be attributed. These isl- ands are in a latitude corresponding to the rude regions of Labrador, and yet cattle pass the winter there in the midst of fine pasture.
In North America, at the base and on the slopes of the Rocky Mountains, where the Mis- souri takes its rise, there is a phenomenon ob- servable that must be ascribed to the heat disen- gaged by the great condensation that takes place
76 METEORS AND METEORIC PHENOMENA.
when the western winds of the Pacific strike the summits of the chain. In winter, navigation is open on the upper part of the river, while lower down it is entirely closed by the ice. At a very considerable elevation, a spring temperature is enjoyed, and the country is covered with rich verdure, at the very moment when the severest cold prevails in the distant plains below.
FORMS OF THE SNOW.
When a current of very cold air penetrates to a warm apartment suddenly, it may produce snow, if the room be full of watery vapor. The story is told that, upon one occasion in St. Peters- burg, a pane of glass was accidentally broken in the window of a saloon where a large party was assembled, and a gust of wind bursting in through the orifice, congealed the vapors of the room and scattered them over the astonished guests in the shape of snow-flakes. Similar effects have been noticed in Siberia and Nova Zembla.
Whenever the temperature of the clouds falls below zero, their drops congeal and form snow, which then falls through the air in flakes until it strikes the ground. These flakes, when caught upon a black surface and examined through the microscope, exhibit a remarkable regularity of
FOKMS OF THE SNOW.
77
form that long since attracted the attention of observers. Kepler speaks of their structure with lively admiration, and, since his day, these grace- ful crystallizations have been described with care.
FORMS OF SNOW-CRYSTALS.
Yet, notwithstanding their great variety, they de- pend upon extremely simple laws. " These snow crystals," says Tyndall, " being formed in a calm
78 METEORS AND METEORIC PHENOMENA.
atmosphere, are constructed on the same model : their molecules group together to form hexagonal stars. From a central nucleus project six needles that, together, form an angle of 60 degrees. From these central needles there shoot out other small- er ones to the right and the left, in their turn de- scribing with infallible fidelity their angle of 60 degrees. These six-leaved flowers assume the most varied and wondrous forms. They are pat- terned in the finest gauzy films, and all around their angles are sometimes seen rosettes of still more microscopic dimensions. Beauty superadds itself to beauty, as though, when once at work, Nature took pleasure in showing, even in the nar- rowest sphere, the omnipotence of her resources." The temperature, the humidity, the degree of motion in the air, modify these crystallized fig- ures. Flakes that fall at the same time generally have the same shape ; but, when there is an in- terval between the falls, a new variety is found each time.
FLOWERS UNDER THE SNOW.
In years when the snow has remained long upon the ground, the watercourses are more abundant, and the harvests more certain. Win- ters at the North without snow are calamities
FLOWEKS UNDER THE SNOW. 79
equalled only by springs at the South without rain. Snow acts as a covering, or screen, which, in sheltering the soil, prevents it from being thoroughly congealed, by the radiation of all its caloric into space, in clear, cold nights ; and then, when the thaw conies, it fully saturates the ground.
Between the eternal snows that cover the tops of the Pyrenees and the Alps, and the slopes at their foot, where the vine flourishes, there is a region in which the snow melts at different sea- sons, according to its elevation ; but, in all places, even at great heights, where it remains for six or eight months, when it does disappear it leaves the soil covered with rich herbage that vegetated un- der its shelter, and that offers an abundant pas- ture to the flocks and herds. The green sward thus strengthened is immediately enamelled with a multitude of lovely flowers that had budded be- neath the snow. The attempt had often been made, but in vain, to acclimate these Alpine plants in our gardens, when a florist conceived the idea, which seemed odd enough at first, to place them, during the winter, between the orange and pomegranate trees in his hot-house. The hardy plants brought from a rude region, where the climate is similar to that of Siberia, and where
80 METEORS AMD METEORIC PHENOMENA.
the mercury sinks to 30° below zero, were per- fectly preserved by the process. This was be- cause they found in the hot-house the conditions provided for them by the thick covering of snow that shielded them in their natural haunts. By its diminutive conducting power, the covering in question shelters them from cold, and, above all, from those abrupt changes of temperature that are so injurious to frail organizations. By anal- ogy we may infer how grain is protected by the snow in the furrows of our fields.
GLACIERS AND RIVERS.
An admirable arrangement in the glaciers of the Alps has been made apparent by a series of observations, carefully pursued for several years consecutively, in regard to the mean depth of water in the rivers flowing from them, in each month of the year. " Since much less rain falls in summer than in other seasons," says Jean Reynaud, " and since it evaporates again almost immediately, all the small streams diminish in volume, and some are even dried up altogether ; thus, at last, the main watercourses do not re- ceive from their tributaries sufficient aliment to sustain them. But Nature has arranged a pecu- liar class of tributaries for rivers important enough
GLACIERS AND RIVERS. 81
to require such special provision, and these yield them all the more in proportion as their ordinary resources diminish, and vice versa. These are the streamlets that flow from the glaciers ; and the immensity of the process required to supply them will be comprehended at once, when we reflect that they must necessarily be raised from the mountains above the clouds, in order to take their rise where they do. None but regions lifted up to those prodigious elevations would be in a posi- tion to accumulate such a quantity of snow and ice, and to retain enough of it during the summer, allowing it to melt, little by little. Thus, the hotter the summer and the more extreme the drought in the watercourses of the plains, only the more rapidly and copiously will the deposits of ice heaped up at the fountain-head be made to melt. Consequently the mountain-brooks will be the fullest at the very moment when the others will be most completely exhausted. On the other hand, in spring and autumn, when the abundance of rain causes the streamlets of the valley and the plain to swell in every direction, and tends to raise the rivers above their regular beds, the glaciers, receiving less heat, feed the rills that flow from them less lavishly, and an actual dry- ness results, so far as they are concerned, which
82 METEORS AND METEORIC PHENOMENA.
counterbalances the humidity of the regions lower down. The general result is, that the rivers which are subject solely to the influence of the glaciers are full in summer and shallow in winter ; while those which are cut off from all connection with the reservoirs of the high regions, and are depend- ent upon the rains alone, have the most water dur- ing the cold season and the least in the hot months. Finally, those that have the aid of both the glaciers and the rain, at different times, along with ordinary tributaries and such as flow from the high mountains, have, other things being equal, a more even and steady supply of water than the rest."
HAIL.
Hail is a shower of globules of ice, the size of which usually varies from that of a pea to that of a hickory-nut, but sometimes attains the dimen- sions of an egg, and even of an ordinary apple. It has been remarked that there is nearly always a little accretion of spongy snow in the centre of hailstones. This is their only opaque portion ; the concentric layers that surround it have all the transparency of ordinary ice. The nucleus and its coverings therefore do not seem to be formed in the same manner* Sometimes there fall heavy
HAIL.
hailstones with a snowy centre which are com- posed of rings or layers alternately transparent and opaque. The fine soft hail seen in autumn and winter particularly, the surface of which looks as though powdered with flour, is usually called sleet. It is, properly speaking, a kind of middle formation between hail and snow.
Yolta relates that one night in the month of August, 1707, he picked up, during a storm that burst over the town of Como, several hailstones that weighed nearly ten ounces. Darwin men- tions a tempest on the pampas of South America, where the icy fragments that fell were so heavy as to kill large animals.
We have just spoken of a hailstorm that hap- pened during the night. This is a very rare oc- currence, for it is usually during the hottest hours of the day in summer that hail forms. The clouds that contain it seem to have great depth, and are distinguished from other storm-clouds by their ashy color. Their edges have numerous jagged indentations, and circular movements are sometimes remarked in them. Hail usually pre- cedes storms of rain, and sometimes accompanies them ; but it scarcely ever follows them, especial- ly when the rains have lasted for any time. In the tropics, hailstorms have been noticed only on
84 METEORS AND METEORIC PHENOMENA.
the lofty mountains. None falls in the plains. It is more particularly frequent in the temperate zone, and then becomes more and more rare as we advance toward the polar regions.
In most cases, the phenomenon of hail has a local character. It is very frequent at the outlet of the deep valleys of the Alps and upon the lower acclivities that separate them from the plains. The low lands of Borgo-franco, near the Yal d'Aosta, are scourged by it every year; At Clermont, at the foot of the Puy-de-D6me, hail falls very often, while on the heights, half a league distant, but one fall of hail has been re- corded in the last twenty-three years! Some- times there are great storms during which hail falls over a vast extent of territory, but these are fortunately rare.
The formation of hail has been more easily explained since the discovery by aeronauts of very cold atmospheric layers (the thermometer mark- ing 40°) at heights comparatively limited, and that too in midsummer. These layers, as we have already said, are filled with fine needles of ice, which, when packed together, may form the nu- cleus of the hailstones, upon which the vapors solidify themselves in other layers. The exist- ence of whirlwinds, arising from the collision of
HAIL. 85
opposite currents — chiefly equatorial and polar — explains the suspension and even the ascension, by a spiral movement, of the hailstones that form. Leaves and twigs, torn from trees by a tempest, have been seen to fall at a distance, covered with a coating of ice.
The currents originated by these whirlwinds are generally in opposite electrical conditions be- fore they become mingled. Hence it is remarked that it rarely hails without thunder being heard, and that during such a fall the electricity de- veloped varies not only in degree but in kind.
Some years ago, rows of long poles were planted in the fields in France to serve as hail- rodsy or protectors against the hail. They were intended to modify the electrical conditions of the atmosphere ; but the system was found to fall short of the purpose, and Arago, in arguing against it in one of his learned " Notices," advises farmers to give more of their attention to mutual cooperative associations, until science shall have discovered some better defence against the rav- ages of the storm.
CHAPTEE IY.
PHENOMENA OF THE GLACISES.
Meteorology of the Glaciers.— Their Formation.— The Grindelwald and Furca Glaciers. — Amphitheatres.— Neves.— Moraines.— Movements of the Glaciers.— Primitive Glaciers.— Polar Glaciers.— Variations of the Seasons and Climate.
METEOROLOGY OF THE GLACIERS. THEIR FORMATION.
WE have already spoken of the favorable in- fluence of glaciers upon the mean height of the watercourses during each season. In a remarka- ble note appended to the work on " Meteorology," by Kaemtz, M. Chas. Martins, one of the most learned professors of the day, summarily examines the influence of temperature and aqueous meteors on these solid rivers that, issuing from the region of external snow, descend slowly into the plains, in the midst of forests and cultivated fields.
" If we examine the phenomena presented by the glaciers," says M. Chas. Martins, " in a pure- ly meteorological point of view, we shall see that
METEOEOLOGT OF THE GLACIERS. 87
it is not too rash to maintain that a time will come when we shall be enabled to judge the modifications of the atmosphere by those of the glaciers, and vice versa. But in order thus to establish in a positive manner the link that unites the meteorology and the physical exterior of the globe, it is desirable to make a long series of meteorological observations in the vicinity of the glaciers, so as to bring the two kinds of phenome- na into direct rapport"
Before making known some of the modifica- tions indicated in this passage, we must pause for a brief space to consider the formation of the glaciers. This is the point of departure recom- mended by M. Martins for the desired observa- tions.
When, in summer, the clouds disperse, after the tempests of rain that fall in the plains, the summits of the mountains are seen whitened with newly-fallen snow, which melts very quickly in the sun, but remains on the highest peaks, in the region of eternal snows, as low down as a certain limit that varies according to the country and the exposure. This limit, when traced upon an ex- tended chain of mountains, appears to be almost horizontal ; but, at certain points in the depth of the valleys, the glaciers are seen descending in long
88 METEORS AND METEORIC PHENOMENA.
white trains to the plain. M. George Altmann, in his " Treatise on the Icy Mountains of Switzer- land," has given the following description of the Grindelwald glacier, so often explored by natural- ists:
THE GRINDELWALD AND FURCA GLACIERS.
" The village of Grindelwald is situated in a long and narrow gorge of the mountains. From, that point we begin to get a glimpse of the glacier, but, in order to see it in its full extent, we must go higher up. Then one of the finest spectacles that can be imagined is revealed. It is a sea of ice, or an immense expanse of frozen water, which descends into the valley along the slope of a lofty mountain. From this frozen reservoir starts a prodigious mass of pyramids heaped together, forming a kind of curtain that occupies the whole breadth of the valley, an ex- panse of about eight hundred yards, and is bor- dered on both sides by lofty mountains, covered with verdure and a forest of pines up to a certain height. This accumulation of pyramidal forms looks like a sea agitated by the winds, the waves of which have been suddenly congealed by the frost ; or, rather, one beholds an amphitheatre formed by an immense assemblage of icy hillocks
THE GKINDELWALD AND FUKCA GLACIERS. 89
of a bluish color, and each of them from thirty to forty feet in height. The point of view is of marvellous beauty. Nothing is comparable to it, especially when, in summer, the sun darts its rays upon this group of glittering pyramids. Then the entire glacier begins to smoke, and glows with a brightness that dazzles the eyes."
We will add to this description the account of the Furca glacier given by Coxe in his " Letters on Switzerland":
" After long efforts and a toilsome march over immense stretches of snow and ice that came in our way, with precipices and torrents constantly beneath our feet, we reached the upper part of the valley by an extremely steep ascent. The great number of forked and irregular masses of rock which, accumulated around this valley, stud the summit of the eminence, have, it is said, originated the name now given it of the Forks or Furca. The region in which we then were, appeared more frightful and desolate than even the most desert parts of Saint Gothard. Below us, it is true, the mountains were clad in rich verdure, and bestrewn with fragrant flowers ; but vegetation did not reach to the height where we were. The most savage sterility surrounded us, and near by there rose a fearful accumulation of ice, from which
90 METEORS AND METEORIC PHENOMENA.
there descended a cataract that, rolling toward the Yalais, is no doubt one of the sources of the Rhone. This glacier was on our left and a little above us, and never did any mass of objects, how- ever grand or terrible, present to us a combina- tion of beauty at once so terrifying and so sub- lime.
" From that point we descended a mass of broken rocks which, in every direction, bristle the ridges of a long line of precipices. I then felt sufficiently fatigued to require rest and refresh- ment. We seated ourselves on the banks of a very limpid streamlet which flowed briskly down the mountain, the latter being so steep that our little repast had to be propped to prevent it from rolling away from us. Before us the Furca gla- cier lay extended in all its beauty. It is an im- mense mass of ice that spreads out, in the form of an amphitheatre, between two heaps of rocks more jagged, if possible, than any that we saw in the neighboring mountains. This amphitheatre en- tirely fills the precipice that separates them, and , rises gradually from their base to a short distance from their summits. The sun, which darted its rays perpendicularly upon the glacier, gave it the brightness and transparency of crystal, while the shadows of its vast fragments, admirably colored,
CIRCLES, NEVE, ETC. 91
intersected its dazzling whiteness with all the varying tints of a truly celestial blue. Terrible cracking noises, indicative of new crevices form- ing in the glacier, were heard several times ; and the Rhone, pouring along at its feet in the form of a torrent, mingled its continuous roaring with the din. It is in a great measure to the accumu- lation of ice that I have just described that the river owes its existence."
CIRCLES. NEVE. MORAINES.
Ramond, the naturalist^ the intrepid explorer of the Alps and Pyrenees, and the translator of Coxe's book, has added to his translation some ex- cellent observations on the glaciers, and has been one of the first to point out a part of the causes that concur in their formation and determine their progress. Before him, Haller, De Saussure, and De Luc, had already established a number of important facts. But it is to more recent re- searches that we owe the explanation of most of the phenomena connected with the nature and movement of glaciers.
" Snow accumulates around the high peaks in deep depressions known as amphitheatres. It is in descending from these amphitheatres toward
the valleys that the snow is transformed, under 5
92 METEORS AND METEOKIO PHENOMENA.
the influence of the sun and nocturnal frosts, tc small grains of transparent ice, and that this granulated mass, called neve in Switzerland, be- comes converted, by pressure and successive con- gelations, to a moving mass of ice, sometimes white and filled with bubbles of air, and some- times more compact and skyey blue."
Such is the origin of the glaciers, which their own weight causes to advance slowly in the direc- tion of the declivities. Huge crevices are pro- duced during this movement, and the water that drips down into them when the snow melts, accel- erates it by hollowing out cavities in the lower- most parts of the mass. Besides, when the water thus contained in the glacier dilates by a new congealment, the entire mass increases in volume, and extends in the direction where it finds the least resistance, that is to say, from the higher point to the lower. This continual progression of the glaciers has been proved by incontestable facts.
A bed of pebbles and sand being interposed between the bottom of the glacier and the rock, the result is, that the action of the masses of ice in movement polishes the surface over which they descend, and makes creases and furrows running in the same direction. This effect has been well
CIRCLES, NEVE, ETC. 93
ascertained, not only in the ice-caverns that are sometimes found at the extremities of the glaciers, but also on the rocks that border them. These rocks, rounded by the ponderous effort of the mass that presses them, often assume a particular aspect, which renders them distinguishable at a distance, wherever a glacier has worn itself a bed. Some of these, seen far away, look like flocks of sheep, and for this resemblance De Saussure the naturalist has invented the term rockes mouton- nees, or " sheep-shaped rocks."
Another order of phenomena demands our attention. As M. Martins has well said, in his " Eesearches on the Glacier Period," " The Alps are immense ruins. Every thing conspires for their destruction ; all the elements seem to have combined to bring down their proud summits. The masses of snow that weigh upon them so heavily in winter, the rain that filters in be- tween their beds in summer, the sudden action of torrents, the less abrupt but still more power- ful operation of chemical affinities, wear away, separate, and decompose the hardest rocks. Their debris falls from the upper heights, into the am- phitheatres occupied by the glaciers, in the form of considerable land-slides, accompanied by a ter- rific uproar and immense clouds of dust. Even
94: METEOES AND METEOEIC PHENOMENA.
in midsummer I have seen avalanches of stone precipitate themselves from the uppermost sum- mits of the Schreckhorn, and form upon the hith- erto spotless snow a long black streak, made up of enormous blocks and a countless number of smaller fragments."
These blocks, some of which measure from ten to twenty yards in thickness, either way, are borne along by the glacier, and consequently form long streaks, which skirt across its borders, or accumulate in transversal lines at its extremi- ties. These streaks of debris^ left by the ava- lanches and land-slides, have received the name of moraines.
MOVEMENTS OF THE GLAOIEES. PEIMTnVE GLACIEES.
By these interesting observations, not only has the movement of the glaciers been circum- stantially proved, but we have been enabled to demonstrate their ancient extent by the furrows grooved in the rock by the primitive glaciers, and by following in the valleys the traces of their lat- eral and transversal moraines.
Thus, the glaciers of Mont Blanc once extended from Chamouni to Geneva. On the eastern slope of Jura there are found isolated bowlders, or wan- dering Hocks, so called, of granite, which can have
MOVEMENTS OF THE GLACIERS. 95
come from no other source than the mountains of Switzerland, the Jura chain being composed of calcareous stone. The immense glacier, which transported these blocks to the height of a thou- sand yards above the level of the sea, extended across the plain that is comprised between the Alps and the Jura. It was, in Martins's opinion, the principal glacier of Switzerland, the others, which are also indicated by the plainest traces, being but its tributaries.
To Jean Perraudin, a chamois-hunter, the first idea of this cataclysm is due. A learned geologist, M. de Charpentier, to whom he had communicated the result of his observations, made it the subject of persevering research, and obtained the most incontestable proof of the grand phenomenon which had been pointed out to him. The study of the glacier period is thus connected with the revolutions of which our globe has been the theatre. Numerous scientific works, among which we must mention in the first rank those of M. Agassiz, have indicated in the two hemispheres the same traces of antediluvian glaciers, extending over the wide plains that sur- round our mountain-ranges.
Professor Tyndall, in his fine work on " The Glaciers of the Alps," attributes the present con-
96 METEORS AND METEOEIO PHENOMENA.
formation of the Alpine chain, in a great measure, to the movements of those prodigious masses of ice which have traced immense furrows in the rock, hollowed out the valleys to great depths as they passed, and by this very action prepared their partial destruction. In fine, Mr. Tyndall explains that the currents of warm air that rise from the valleys toward the heights, have a temperature the more elevated and a force the greater the deeper the valley is. Hence it results that the glacier grows smaller as it sinks lower, and that it reaches limits at last which it cannot pass. This equilibrium between the thaws of summer and the increase and advance of winter appears to be established at the present day, and, with some rare exceptions, we know the mean limit beyond which the ice never goes.
We find among the Pyrenees, the Yosges, the mountains of Scotland, and the principal ranges on the globe, the same traces of an immense de- velopment of primitive glaciers. We are igno- rant, as yet, of the cause of this phenomenon, super- induced, as it was, no doubt, by meteorological conditions very different from those now ex- isting, but which persevering observation of the disturbances taking place under our eyes will perhaps enable us to discover. Thus, Professor
MOVEMENTS OF THE GLACIERS. 97
Frankland, of the Royal Institution of London, lias recently shown that the limit of the eternal snows is higher in the interior of continents than in the vicinity of seas. It may be readily under- stood, in fact, how an abundant production of watery vapor is one of the principal causes of the formation of glaciers, the vapor becoming snow and ice in the high regions of the atmosphere. But the abundance of aqueous meteors is also in correspondence, as we have seen, with the temper- ature, so that it is impossible to admit the exist- ence of the immense glaciers of which the traces and deeply-worn channels are found on all sides, at the very period when the mean temperature of the globe was above the present temperature. The chains of mountains, which had just then ap- peared, had not yet been encroached upon by the slow but potent action of the different agents of destruction that excavate and reduce them, and those primitive chains presented a vast surface for the accumulation of snow and ice, the forma- tion of which was favored by the more frequent vicinity of great lakes and interior seas, such as the ancient sea of Sahara, indicated by Charles Lyell in his " Principles of Geology."
Maury, in his excellent researches on the geo- logical part performed by the winds, has put in
98 METEORS AND METEORIC PHENOMENA.
the way of completion some important discoveries regarding the relations that subsist between the quantity of moisture set in circulation by the at- mosphere and the configuration of the seas and continents. The action of the great aerial cur- rents, as well as that of the great oceanic cur- rents, varies with the circumstances that favor or obstruct it, and these variations are in close re- lation to the distribution of heat upon the globe. It is to these causes, which are still incessantly at work, that Mr. Lyell attributes also " the principal revolutions of the meteorological condition of the atmosphere at different geological epochs."
The conflict of the elements, subjected, accord ing to the region, to the influence of heat and cold, necessarily produced convulsions correspond- ing in extent and intensity to the greater or less power of these influences, and left on the surface of the globe the deep traces that science discov- ers there to-day. " The phenomena," says M. Martins, " have remained the same ; but, instead of those gigantic manifestations characteristic of the geological epochs preceding our own, they re- strict themselves to the limits of action which have been imposed upon them by the equilibrium of the period of repose that the coming of man has inaugurated on the earth."
POLAR GLAGIEKS. 99
POLAR GLACIERS.
The limit of the eternal snows descends lower in passing from the equator to the poles, from the glaciers of the Cordilleras that cover the volca- noes of Peru, to those of Spitzbergen, which come down to the edge of the sea, and fill up the bottom of the bays. These last-mentioned gla- ciers present a remarkable peculiarity. Upon the western coast of the island, bathed by one of the branches of the great lukewarm current of the Atlantic — the Gulf Stream — the sea thaws during the summer, and melts the lower part of the glaciers, which, continually advancing, at length pass beyond the shore. The parts which are no longer supported below are then seen de- taching themselves and forming the field-ice that is met with in such quantities in the Arctic Ocean. Madame Leonie d'Aunet has described this phe- nomenon, as follows, in her interesting " Yoyage to Spitzbergen" :
" During my sleep the thaw had commenced, and the physiognomy of the day had changed as though by a miracle. A spectacle of the utmost turbulence and agitation had succeeded to the motionless solitude of the evening before. A flotilla of islands of ice surrounded the corvette,
100 METEOBS AND METEORIC PHENOMENA.
and covered the bay as far as the eye could see. The ices of the pole, which no dust has ever soiled, as pure now as on the first day of the creation, are tinged with the most vivid colors. One would say the rocks were precious stones. One sees the sparkle of the diamond, and the dazzling hues ol the sapphire and the emerald, blended in an un known and marvellous substance. These floating islets, incessantly undermined by the sea, change their forms at every instant. By an abrupt movement their base becomes their summit; a needle changes to a mushroom; a column imi- tates an immense table; a tower is transformed to a staircase. And all this is so rapid and un- expected that one cannot help thinking that some supernatural power must control the sudden transformations. At all events, from the first moment, I fancied that I saw before me the ruins of a fairy city suddenly destroyed by a supe- rior power, and condemned to disappear without leaving a single vestige where it had stood. I saw fragments of architecture in every style and of every period dashing together around me — belfries, columns, minarets, ogives, pyramids, turrets, cupolas, crenellated battlements, volutes, arcades, pediments, colossal masses of masonry, carvings as delicate as those that encircle the
VARIATIONS OF THE SEASONS AND CLIMATES. 101
slender pillars of our cathedrals — all there con- founded and commingled in one common dis- aster. The palette could not reproduce, and mere description cannot convey, an idea of this strange and wondrous combination.
" This place, where every thing is cold and inert, is represented as being wrapped in a pro- found and gloomy silence, is it not? Well, a totally different conception of it must be formed. Nothing could reproduce the tremendous tumult of a day of thaw at Spitzbergen.
" The sea, studded with sharp pinnacles of ice, plashes noisily ; the tall masses bristling along the coast slide down, break from the rest, and plunge into the gulf with a terrific crash ; the mountains crack and split apart ; the waves dash furiously against the granite capes ; the islands of ice as they break up make a succession of crackling sounds like discharges of musketry, and the gust tosses whirling clouds of snow on high with hoarse roarings. It is terrible ! It is magnificent ! One seems to hear the choirs of the abyss of the old world intoning the prelude to a new chaos."
VARIATIONS OF THE SEASONS AND OF CLIMATES.
We have seen how the melting of the glaciers maintains the volume of the rivers during the
102 METEORS AND METEOEIO PHENOMENA.
summer-time, and thus, in keeping up the water- courses, contributes to refresh and fertilize our fields. The floating ices of the pole, which then descend toward our latitudes, also moderate the heat of our summers by the influence of winds and currents. Sometimes, even, as a learned meteorologist, M. Renou, has remarked, a cold summer like that of 1816 may be the conse- quence of a great breaking up of the polar ices.
The regions adjacent to the two poles may be considered as immense glaciers, resting upon rocks of greater or less elevation, and sometimes upon lofty mountains, the summits of which pierce the snow. Two volcanoes, the Erebus and the Ter- ror, were discovered in 1841 by Sir James Ross, during his expedition to the Antarctic regions. The Erebus, which is about 12,000 feet in height, and covered with snow to the crater, threw out dense volumes of smoke at intervals.
A knowledge of the causes that, in these regions, determines the periodical increase or diminution of the ice, would be of great interest for the general meteorology of the globe. These variations seem to be connected with a variation of seasons dependent upon the periodicity of the solar spots, as M. Renou indicates, or on the movements of the earth, in its orbit, as hinted by
VARIATIONS OF THE SEASONS AND CLIMATES. 103
Jean Reynaud, when referring to the secular va- riation of climates in his u Terre et Ciel." But a long series of observations on the glaciers of both hemispheres would be necessary, in order to solve these important questions with any certainty.
Already numerous discoveries, due to the in- trepid zeal, the devotion, and the scientific skill of the great explorers who penetrated the icy soli- tudes of the pole, and the burning deserts of the equator, or climbed the perilous summits of our highest mountains, have opened new horizons to investigation. In the vast totality of meteoric phenomena, until then so confused, we have, through their aid, seen a few simple laws stand forth that shall hereafter serve to guide us in studying the perturbations of the atmosphere and the modifications that they lead to on the surface of the globe.
CHAPTER Y.
THUNDER-STORMS.
LuminouE Phenomena.— The Fires of St. Elmo.— Thunder-storms among the Mountains.— The Forms of Lightning.— Globular Thunder-bolts.— Thunder.— Singular Effects of Lightning.— Lightuing-rods.— Geogra- phy of Thunder-storms.— Influence of the Soil.— Volcanic Storms.— Action of Thunder-storms upon the Subterranean Waters.— Utility of Thunder-storms.
LUMINOUS PHENOMENA. FERES OF ST. ELMO.
THE air during a thunder-storm is some- times so highly charged with electricity, that it becomes visible in the midst of the obscurity by a vivid light resting on all surrounding bodies, and particularly upon the water. Mention is made of luminous rains, during which the ground seemed to be on fire. More than once travellers have been seized with alarm on seeing their wet clothes all aglow on stormy nights. A curious narrative addressed by M. Allemand, a physician of Fleurier, near Neufch&tel, to Professor Piotet, as mentioned in the Bibliotheque Universelle of Geneva, sets forth a case of this kind :
LUMINOUS PHENOMENA. 105
" On the third of May last, I was called to Motiers about ten o'clock in the evening, and was surprised, so to speak, as I was leaving the vil- lage, by a storm that was quickly followed by a very heavy rain. Although provided with a walking-stick umbrella, I thought I had better close it, as the thunder grew more frequent and severe, and I even held the upper end, which, as you may know, forms a metallic point, in my hand ; the point is blunt indeed, yet it might at- tract the lightning. Ere long, the night, which was excessively dark already, became more so with torrents of rain, and it was only by the help of the vivid and frequent flashes of lightning, that I was able to pursue my way. Thus moving along through the most violent tempest that can be imagined in our part of the country, I sudden- ly noticed a light that appeared to come from above, and, at once raising my eyes, I remarked that it was the brim of my hat that seemed to be illuminated. Thinking that it was real fire, and without taking time to reflect, I suddenly passed my hand along the luminous edge, expecting to extinguish it. But, to my great surprise, it only shone the brighter, and this gave me a confused idea that I had been mistaken as to the charac- ter of the light. My hand was full of water that
106 METEORS AND METEOEIC PHENOMENA.
flowed from my hat, and, in making a motion to shake it off, I saw it shine like a piece of polished metal reflecting a bright light.
" Hereupon, to the sensations that I had ex- perienced until then, succeeded such emotion as caused me to utter half aloud an exclamation of fear. I was then about one hundred paces from the Chaux farm, that is to say, about ten minutes' walk from Fleurier, and fifteen or twenty from Motiers. I deliberated for a moment whether I should seek shelter in the farm-house, or continue on my way ; but, at last, some scientific reasoning in my own mind, and profound reliance upon the Supreme Author of the formidable apparatus by which I was surrounded, decided me to push on. Having been enabled to fill my hand unharmed with the electric water that gleamed along the brim of my hat, I felt emboldened to repeat the experiment — although, after all, I did so the sec- ond time with a sort of fear — and ascertain whether this phosphorescent light had no odor, and whether it produced neither a crackling sound nor sparkles of flame. But I saw only the beautiful light I had remarked in the first in- stance, which did not rise from my hand at the moment when I opened it, but seemed to be ap- plied to its surface like a shining varnish. This
LUMINOUS PHENOMENA. 107
light lasted only for an instant. Continuing on my way, with my gaze almost constantly riveted upon the brilliant halo that bordered my hat, I saw another vivid light on the surface of the smooth handle of my umbrella, at the spot where the me- tallic plate is usually found on which the name of the owner is engraved. My first movement was to pass my thumb over the place, in order to ex- tinguish this new fire, which had become as per- plexing to me as the other. The same phenom- enon ensued ; that is to say, the part rubbing be- came quite as luminous as the part rubbed. I then felt afraid of the umbrella, the metallic mounting of which was continually before my mind, and I threw it down. The thunder-claps increased, although the electric concussion seemed to be, and was, indeed, at some distance from me. Once relieved of my umbrella, I endeavored to rub the rim of my beaver briskly with the sleeve of my coat, but this had no other effect than to make the crown of light more vivid, and I arrived with it at Motiers. I attribute its ces- sation to the proximity of the tall poplars that border the road near that village."
These effects are explained by the influence of the storm-clouds in the upper region of the at- mosphere. The latter attract, at the surface of
108 METEOES AND METEORIC PHENOMENA.
the soil, an electricity contrary to that with which they are charged. Frequently the pencils of rays that one sees at the extremity of the points placed on an electric machine in operation, appear in enlarged dimensions upon all kinds of salient objects, metallic bars and uprights, the spires of belfries, and the masts and yard-arms of ships. Those brilliant little flames, which sailors call the fires of /St. Elmo, indicate the abundant emission of the terrestrial fluid, neutralizing the fluid of the clouds. "We shall cite, in addition to the above, only the following facts, as Arago gives them :
" On January 14, 1824, just after the close of a storm, M. Maxadorf , happening to look at a wagon loaded with straw, in the middle of a field near Gothen, over which hung a huge black cloud, observed that every stalk stood out straight and seemed on fire. Even the whip of the driver threw off a vivid light. The phenom- enon disappeared as soon as the wind had swept away the black cloud, but it had lasted ten min- utes.
" On the 8th of May, 1831, after sunset, some officers were walking bareheaded, during a storm, on the terrace of the Bab-Azoun fort in Algiers, when each of the party remarked with surprise,
STOKMS AMONG THE MOUNTAINS. 109
as he looked at his neighbor, that there were little pencils of light at the ends of his hair. When these officers raised their hands, similar luminous plumes formed at the ends of their fingers."
STORMS AMONG THE MOUNTAINS.
A Swiss engineer, M. Buchwalder, was en- gaged in geodesic operations on the summit of Mont Sentis, at a height of seven thousand five hundred feet above the level of the sea, when he was caught in a violent storm. " Heavy clouds," he says, " coming from the west, enveloped the mountain. Yery soon a violent wind announced a tempest ; thunder was heard in the distance, and the hail fell in such abundance that, in a few min- utes, it covered Mont Sentis with a sheet of ice. "We took refuge in our tent, and I carefully closed all the openings so as to leave no hold to the wind. For a few moments, the storm seemed to abate, but it was only an interval of silence, a res- pite, during which a terrible crisis was in prepara- tion. In fine, at eight o'clock in the morning, the thunder was heard again, but much nearer and more violent, and it continued thus, for hours to- gether, without cessation. Tired of my long im- prisonment under the tent, I went outside, to note the condition of the sky and measure the depth
110 METEORS AND METEORIC PHENOMENA,
of the hail that had fallen. Scarcely had I taken a few steps in the open air, ere the thunder burst over my head with such fury that I deemed it prudent to regain the shelter of my tent, and my aid followed my example. In order to diminish the danger of being struck by the lightning, we lay down side by side upon some planks. At this moment a cloud, as dense and black as night, en- veloped Sentis. The rain and hail fell in tor- rents ; the wind blew with fury, and the flashes of lightning succeeded each other incessantly, crossing and recrossing in every direction, and surrounded us with a lurid light like the reflec- tion of a fire. The crashes of thunder, rebounding from the precipitous sides of the mountain, leaped from echo to echo with such vehemence that we could scarcely hear ourselves speak. The sound was a sharp, rending noise ; a quivering crash, as though the heavens had fallen in, and a dull pro- longed roar, all in one. At length, the fierceness of the storm became so terrible that my companion could not restrain an emotion of alarm, and asked me if we were not in imminent danger of losing our lives. I endeavored to reassure him by men- tioning the fact that Arago and Biot, during their observations in Spain, were surprised by a simi- lar tempest. The lightning had struck their tent,
STORMS AMONG THE MOUNTAINS. Ill
but had glanced off from the cloth without hurt- ing them.
" Hardly had I told him this, ere I heard a cry of distress : l O my God ! ' — and at the same in- stant I saw a ball of fire flash from the feet to the head of my companion, and felt a violent shock in my left leg. Our tent, also, was torn asunder in the middle with a terrific detonation. I turned toward my companion ; the unfortunate man had been struck by the thunder-bolt ! In the light yielded by the tearing open of the tent, I saw the left side of his face dotted with red and brown spots caused by the electric fluid. His hair, his eyelashes, and his eyebrows, were singed and burnt ; his lips and nostrils were a livid blue ; his breast heaved for a moment, and then the sound of his breathing ceased. I was suffering horribly myself; but, forgetting my own mishap in my anxiety to aid my companion, who, I saw, was dying, I called him aloud, I shook him, but he made no response. His right eye, which was wide open, brilliant and full of intelligent meaning, seemed turned upon me to implore my assistance, but the left eye re- mained closed, and, on parting the lids, I saw that it was dull and leaden. I still thought that there was a remnant of life in him, but only for a moment ; three times I tried to close that right
112 METEORS AND METEORIC PHENOMENA.
eye, which was still gazing fixedly at me, and three times it opened again, with all the look of life. I then placed my hand over his heart ; it no longer beat. At last, my grief put an end to this distressing examination. My own left leg was paralyzed, and I felt an acutely painful shivering in it, accompanied by an extraordinary agitation or boiling of the blood. A convulsive tremor ran through my whole body; a general stifling sensation half choked me, and my heart beat in the most tumultuously irregular manner. Was I to perish like my hapless companion ? Thank God, however, I managed to reach the nearest village, after extreme exertion. Subse- quently I discovered that my instruments had been struck by the lightning, for every metallic article that the tent contained when the thunder- bolt fell, bore traces of the passage of the fluid. The points, edges, and most delicate parts, were softened and melted."
THE FORMS OF LIGHTNING. GLOBULAR LIGHTNING.
Sometimes the clouds, during a storm, seem to give out a continual emission of electricity, for they remain luminous a long time, as Rozier, the physiologist, observed, during a storm of great intensity that he witnessed in the environs of
THE FOKMS OF LIGHTNING. 113
Beziers. " Little by little," he says, " a luminous point that made its appearance in the midst of dense clouds, assumed breadth and volume. It then, by imperceptible degrees, formed a zone, or phosphorescent band, which revealed itself to my eyes as about three feet in height ; it at last sub- tended an angle of sixty degrees. Above this first zone, another formed of about the same height, but of not more than thirty degrees' measurement. An open space of about the same extent separated them. In both these belts were noticed irregular- ities similar to those seen on the edges of the heavy clouds that are the forerunners of a storm. These edges were not equally luminous, although the centre of the belts presented a uniform bright- ness. "While they were advancing toward the east, the lightning darted three different times from the end of the lower belt, but without any appreciable detonation." This phenomenon lasted for a quarter of an hour, and was dispelled by a violent gust from the southward, that carried the storm to a distance.
These intermittent discharges of electricity have very varied forms, and traverse the atmos- phere with astonishing velocity. Wheatstone has demonstrated that the most brilliant and ex- tended lightnings — sometimes from fifteen to
114: METEOES AND METEORIC PHENOMENA.
eighteen miles in length — do not last the thou- sandth part of a second. Some consist of very delicate shafts of light, with very sharply-defined borders, describing zigzag lines in space, and sometimes dividing into several branches. Most usually they are white, and sometimes, but rarely, purplish, violet-hued, or bluish.
Others extend, on the contrary, over a wide surface, and have neither the whiteness nor the brilliant illumination of those before mentioned. Their hue is often a very vivid red. "These lightnings," says Arago, " appear, sometimes, to illuminate only the outlines of the clouds from which they emanate. Sometimes, too, their viv- id light embraces the entire superficial extent of those same clouds, and, moreover, seems to issue from the interior of them. One might say with truth that the clouds open. Such is the popular expression, and I should search in vain for others to depict the same phenomenon more accurately."
The first kind of lightning is much more rare than the second. In ordinary storms, hundreds of the latter appear for every one instance of linear, or, more especially, of forked lighting. "We will here quote the description of a remarkable storm observed by M. Liais during his sojourn in Brazil.
THE FORMS OF LIGHTNING. 115
Although it was the 30th of January, the thermometer marked thirty-three degrees. " Dur- ing the night, the wind came up very feebly from the southwest ; in the morning the air was pure, and a burning sun fell upon the soil, still damp with the rain of the preceding days. In the after- noon there were seen some cirri. Toward even- ing other clouds, cumulus and cumulo-stratus formed, and, at sunset, the sky was almost covered.
" At seven o'clock, flashes of lightning were seen in the east, and, at ten minutes past seven, the storm had acquired all its intensity. At that time, zigzag lightnings were darting forth contin- ually, at least one-third of them forked. These flashes were white, and very vivid. Sometimes, they seemed to tend slightly toward a bluish tinge, and, at others, were of an orange hue. They did not form interrupted zigzags, as they do in many storms, but rather broken lines, and, moreover, each of these lines was sinuous. These lightnings did not end in points, but generally presented a slightly-rounded form at the ex- tremity where they terminated. Although these flashes had great velocity, it seemed to me that their development, and the manner of their prop- agation, could be followed with greater facility
than in ordinary storms. Two flashes were very 6
116 METEORS AND METEOEIC PHENOMENA.
rarely seen at the same time, and their emission had a certain regularity.
" The most of these flashes were unaccom- panied by any noise. From time to time we could hear a slight rumbling in the distance, but, owing to its frequency, without being able to dis- tinguish to what flash it belonged. Many of them seemed to issue from a sort of very small cumulus, situated but a little distance above the horizon, and to propagate themselves with an apparent ascensional movement. Others seemed to issue from the upper bed of clouds, with an apparent inverse movement. The storm was not accompanied by rain. Only at the beginning a few large drops had fallen. The upper cloud, upon which the lightnings shot out in relief, did not cover the entire face of the sky, and a few stars could be seen.
" I pass on now to the most singular part of the phenomenon. Besides the two-forked light- nings and those with three or four offshoots, which were also very frequent, not a moment went by without our seeing also what might be termed arborescent or tree-shaped lightning. These were flashes that divided themselves into several prin- cipal branches, which in their turn split off into a multitude of smaller boughs, that again pre-
THE FOKMS OF LIGHTNING. 117
sented the same sinuosities, and the same round- ed endings noticed in the other flashes. There was no other means of counting these branches than by reproducing immediately on paper the impres- sion made on the retina of the eye. One of these flashes, that I had remarked particularly, and that had appeared to propagate itself as it descended, divided, at first into two branches, which subdi- vided in their turn, in such manner as to form fifteen branches in all. Another was of radiating form, and one arborescent, that is to say, its prop- agation was in every direction, but starting from a common centre.
" The tempest seemed to continue motionless. At the end of about ten minutes, the frequency of the flashes diminished ; at a quarter past eight, they ceased, and the clouds soon dispersed. The zodiacal light was seen in the west and the east, below the milky way, spanning the entire sky. It may be well to mention that on the preceding evening the phosphorescence of the sea was ex- traordinary, and such as I had never seen it be- fore. On the evening of the storm, on the con- trary, it had resumed its usual appearance under the tropics."
In another storm, M. Liais again noticed the extremely curving shape of the ends of the arbo-
118 METEORS AND METEORIC PHENOMENA.
rescent flashes, and a still more marked tendency to terminate in balls of fire. Three times these balls broke off, leaving a train of light behind them, like a bolide, and traversing an arc on the sky of thirteen degrees in half a second. We have seen the origin of a third kind of lightning, which the physiologists call globular lightning, without being able, up to the present time, either to ex- plain it or to imitate it, as they do with ordinary lightning. It is entirely analogous, excepting in dimensions, to the sparks of an electric battery. These globes of fire, which are sometimes as large as a bomb, descend to the ground with a motion slow enough to enable the observer to note their shape. Their color varies from dead white to vivid red. In advancing along the soil, they seem to keep aloof from the surface of objects and emit no heat. They are sometimes seen to stop for an instant, then to advance again, and then rebound, like an elastic ball, or divide into several smaller globes. Sometimes, at the end of their course, a plume seems to issue from them, and then they explode with a noise like that of a cannon, hurling zigzag lightnings on all sides of them, that produce the most fearful ravages.
THUNDER. 119
THUNDER. SINGULAR EFFECTS OF LIGHTNING-STROKE.
The sound caused by a single flash of light- ning sometimes lasts without interruption as much as forty-five seconds. Although it is true that all the beds of air lying along the course of the im- mense electric spark are shaken, so to speak, at the same time, the sound developed at each point reaches the observer only by successive concus- sions, and the difference in distance produces the variations noticed in the violence of the thunder, its rolling reverberations, and its sudden crashes, repeated again and again by the echoes. The discharges that take place between a cloud and any terrestrial object are the most severe.
We cannot account for some of the phenom- ena of transporting power revealed by lightning, unless we call in some other force than electricity. It was beyond all doubt the power of steam alone, eliminated on its passage, which could, for instance, lift a wall weighing twenty-six tons, and carry it in one mass a distance of many yards. Repeat- edly, the roofs of huge edifices have been swept off as though by the explosion of a mine.
In passing through bodies, the lightning very rapidly raises their temperature. Metallic con- ductors nearly a third of an inch thick have been
120 METEORS AND METEORIC PHENOMENA.
melted by it, and, when of less dimensions, have been completely volatilized. Bell- wires are found incrusted in tiny drops in the floor, or shot in fine dust over the walls.
Travellers often see the surface-beds of rock on the tops of mountains vitrified by the lightning. When it penetrates beds of sand it forms tubes of melted and adhering quartz, sometimes thirty and forty feet in length, which have received the name si fulgurites. The following fact is cited by M. Jamin : " On the 17th of July, 1823, the lightning struck a birch-tree, near the village of Rauschen, on the borders of the Baltic. The in- habitants, who hurried to the spot, saw two deep, narrow holes close to the tree, and one of them seemed warm to the touch, notwithstanding the rain. Professor Hagen, of Koenigsberg, caused the ground around the holes to be dug away with great care. The warm one presented nothing peculiar ; the other also, for the depth of a foot or so, offered nothing remarkable, but a little lower down commenced a vitrified tube. The fragility of the tube, however, did not admit of its being taken out in pieces over an inch or two in length. The inside glassy lining was very shiny, of a pearl-gray color, and studded with black points along its entire extent."
LIGHTNING-RODS. 121
Masses of iron and steel traversed by lightning become magnetic, and numerous observations show that, on board of vessels that have been struck, the compasses have been made to deviate from their normal direction. Trees, which are excellent con- ductors, because of their moisture, are often struck. In such cases, where the burning of the tree has not ensued, the trunk is seen to be dried up and divided into long strips. Inside of houses, all combustible bodies take fire on the passage of lightning through them.
LIGHTNING-BODS.
The identity of electricity and lightning was proved by Franklin. " In order to verify a con- jecture he had formed on the subject," says Mignet, one of his biographers, " he undertook to draw electric fluid from the clouds. The first means that occurred to him was to erect point- ed iron rods that might attract it This device not seeming practical to him, upon mature reflec- tion, because he could not find any place suffi- ciently high, he conceived another. He constructed a kite of two pieces of stick, covered with a silk handkerchief. The longer stick he terminated with an iron point at its upper extremity. He then tied to the kite a hempen cord ending with
122 METEORS AND METEORIC PHENOMENA.
a silk one. Where the hempen cord, which was a conductor, and the silken one, which was not, joined, he fastened a key, so that the electricity might accumulate there and throw off sparks an- nouncing its presence. With his apparatus thus prepared, Franklin went out to the fields one day during a storm. His kite, carefully secured by its string, which was in its turn made fast to the silk cord, was given to the air, while Franklin himself stood aloof and watched it with anxiety. For some time he saw nothing, and was afraid that he had been mistaken ; but, all at once, the string at both ends stiffened and the key became charged. It was the electricity descending. Franklin hast- ened to the spot where he had secured the string at the lower end, presented his finger to the key, and received a smart shock that might have killed him, but, as it was, only filled him with delight." By the invention of the lightning-rod, Frank- lin proposed to neutralize the effects of thunder- clouds by furnishing them with an electricity the opposite of their own. He protected buildings with long metallic rods, terminating in sharp points at the top, and communicating with the ground. Along these the terrestrial electricity escapes toward the overhanging cloud, and neu- tralizes it more or less rapidly. Sometimes, dur-
LIGHTNING-RODS. 123
ing the night, tall plumes of electric light are seen shining on these points. It may happen that the cloud is not sufficiently discharged, and the light- ning may strike between it and the edifice. How- ever, in that case, it falls upon the stem of the rod, which is connected with the ground by an isolated conductor.
The efficacy of lightning-rods is fully demon- strated by statistics. Mr. Snow Harris reports, for instance, that in Devonshire six churches with tall steeples having been struck, one of them only, that was protected by a lightning-rod, suf- fered no damage. The Church of St. Mark at Venice, the Valentino palace at Turin, the tower of Sienna, all in cities where the lightning causes frequent damage, have likewise been pre- served by lightning-rods.
"We well remember the terrible thunder-storm that burst over the city of Strasburg on the 14th of August, 1833, about four o'clock in the after- noon. The tower of the cathedral was struck three times in the space of a quarter of an hour. At the last stroke, the whole pile appeared to be in flames for some seconds. In many places, the lead, the copper, the iron, and even the mortar were found to be melted, or vitrified. Fragments of metal had soldered themselves to the bells, and
124: METEOES AND METEORIC PHENOMENA.
it was found difficult to detach them. Yery large masses of stone fell in the neighboring streets. In the next year, one of the turrets was cut in two by the lightning, and it was at last decided to put up lightning-rods on the spire and other parts of the edifice. Since that time, it has been re- marked, as a matter of fact, that it has been struck by harmless discharges only, which fell on the rods and followed the conductors into the ground, without the least deviation. Moreover, thunder-storms appear to have become less fre- quent and less intense over Strasburg.
Let us, also, mention the following instance, where, as Arago phrases it, " Mature was caught in the act." " On the 21st of May, 1831, during a very violent thunder-storm, the ship Caledonia was under sail in Plymouth Bay. From the town, the lightning could be seen darting toward the water, at but a short distance from the vessel. It fell also on the shore and there caused several accidents. Surrounded, as it were, by these fall- ing thunder-bolts, the Caledonia, protected by her lightning-rods, yet escaped all harm and sailed along as safely as though the sky had been clear."
Extreme care, as recommended by all our learned associations, but too often neglected, is required in the construction and keeping of the
LIGHTNING-BODS. 125
lightning-rod. It is of special importaDce that the point should be of metal that will not oxidize, and that the conductor should be united with iron ligatures to all the large metallic pieces of the structure, and be in perfect communication with the ground. In damp soil, the electric flow and dispersion are very easy, but the iron rusts and is quickly worn out. In a dry soil, there would be insulation, and great mishaps might be appre- hended. The conductor in such a case must be made to run into a pit full of slacked cinders ; coal, when it has been red heated, being an excellent conductor, while it has the additional good prop- erty of not attacking iron. When there is a nat- ural sheet of water in the vicinity, the conductor might be led into it, and provided with numer- ous branching pieces where it does so. A reser- voir or cistern cannot be considered in the same light as a well or pit, properly speaking, since, the stone blocks and the cement that line its bot- tom and sides yield but difficult passage to elec- tricity ; there is no free dispersion, and a violent concussion might ensue.
The difference in the conducting power of different soils, and of the bodies placed there, should, as well as their form, direct the choice of localities in which one is the least exposed to be
126 METEORS AND METEORIC PHENOMENA.
struck by lightning. According to the considera- tions presented in the foregoing pages, care must be taken not to get under trees, or to go too near to large metallic masses, or very high build- ings.
Men and animals have been killed beneath a thunder-cloud, without being struck directly by lightning. This phenomenon, called the re- turn-stroke by physiologists, is explained by the influence of a very extensive electrified cloud, discharged at one of its extremities by lightning. If, at that moment, then, bodies, beneath the other extremity being powerfully influenced, re- turn suddenly to their natural condition, they experience a very violent shock.
THE GEOGRAPHY OF THUNDER-STORMS.
Humboldt found vitrified surfaces, caused by lightning, on the summit of the mountain of Toluca, at the height of 13,860 feet above the level of the sea. This fact does not prove that thunder-clouds can attain that elevation, for there are cases on record where lightning has struck the tops of mountains, starting from their base. On the other hand, again, the inhabitants of Chamouni affirm that thunder-storms have passed over the summit of Mont Bknc, which is 14,430 feet high.
THE GEOGRAPHY OF THTJNDER-STOKMS. 127
Arago gives 228, and even 91 feet as the lower- most limit, which, according to exact measure- ment, can be assigned to thunder-storms.
The principal elements in the geographical distribution of thunder-storms are in relation with the distribution of rain. Kearly all the rain of the tropical regions falls from thunder-clouds, and under the equatorial belt one hears the rumbling of thunder almost continuously. At Calcutta sixty thunder-storms per annum are counted, and among them forty-five occur during the southwest monsoon, that is to say, from April to September. There are none from November to January, or during the northeast monsoon. We have already referred to the exceptional case of Peru, where the inhabitants have never heard thunder.
In the zone of tropical calms, thunder-storms are frequent ; less so, however, than under the equator. The example of Europe may give an idea of the state of things in the middle latitudes. In southern Spain there are the same number of thunder-storms, say, from five to ten, as in Eng- land and Scandinavia. Italy, the Adriatic Sea, and Greece, present the maximum of the European ratio of thunder-storms. Janina and Rome have forty-five and forty respectively per annum. Among the Alps about thirty are counted. In
128 METEORS AND METEOKIO PHENOMENA.
France and Germany there are from fifteen to twenty. In the latter country, however, certain localities, such as Munster, Braunsberg, etc., which are exposed to frequent thunder-storms, are re- markable exceptions to this rule. It is in the Adriatic, and. upon the western coasts of Europe, that the winter thunder-storms are most frequent. As we advance toward the east, they become less numerous, and, beyond the frontiers of Germany, only summer thunder-storms are noticed.
In the high latitudes, thunder-storms are ex- tremely rare. Sometimes as long a period as six years will pass without thunder being heard in Greenland. Farther on we shall state how the thunder-storm is replaced in those regions by the splendid phenomena of the aurora borealis.
In the tropics, thunder-storms are always caused by ascending atmospheric currents, and the same is the case with the summer thunder- storms of the temperate zones. They take place every afternoon, when the arrangement of the country is favorable to them. Above some of the lakes of Switzerland there thus daily appears a small cloud that moves over and fixes itself on the slope of a neighboring mountain, and then bursts with a terrific concussion. We have no- ticed this periodical formation of thunder-storms,
THE GEOGRAPHY OF THUNDEK-STOEMS. 129
toward the close of summer, in the bays of Naples and Tunis.
The thunder-storms of the temperate zone usually accompany the heavy rains that result from the meeting of the equatorial and the polar currents. There then ensues a struggle between the two winds that often lasts for several days, and the result of which determines the state of the weather. With the south winds, the air be- comes heavy, warm, and damp, and dense clouds ascend along the horizon. But suddenly the northern gust sweeps down, accompanied with electric explosions. The fluctuations of these currents occasion several consecutive thunder- storms, which exhibit no periodicity, and are of very variable duration. Should the polar wind prevail, all the vapors dissolve in rain, or are borne off to a distance, and the sky clears up again. Upon other occasions, it is the north wind .that rules at the outset, with clear, dry, and cold weather, which the arrival of the south wind changes. This current is indicated in the high latitudes by the cirrus, which rapidly grows more dense, changes to cumulus, and covers the sky with a thick veil of clouds, whence the lightning soon begins to play. When the north wind yields, the thunder-storm winds up with mild weather and
130 METEORS AND -METEORIC PHENOMENA.
those long rains that are so powerful a source of fertility in the temperate zones.
INFLUENCE OF THE SOIL. VOLCANIC THUNDER- STORMS.
According to some meteorologists, the nature of the ground may contribute to the frequency of thunder-storms. "In the department of May- enne " (in France), says M. Blavier, a mining- engineer, " there exist masses of diorite (a species of rock in which loadstone is sometimes found), which contain a notable proportion of iron, and affect the needle of the compass. We were as- sured that in certain parishes, such as Niort, for instance, the most threatening thunder-clouds would be seen to disperse as they drew near, or to turn aside in certain directions. We think that the conducting force of several considerable masses of diorite will explain this phenomenon." The savant Yicat reports the following observation, made at Grondone, a village situated among the Apennines, near a very rich iron-mine, that rises in the form of an isolated peak. " Nearly every day, in the months of July and August, an electric cloud is seen forming above this region. The cloud, growing larger by insensible degrees, re- mains for some hours suspended over the mine,
INFLUENCE OF THE SOIL. 131
and then, in bursting, discharges itself toward the peak, which is almost entirely metallic. The miners," adds Yicat, " instructed by experience, judge when it is time to quit the spot. They, at the right moment, retire some distance, and then return to their work after the explosion. I have frequently seen the great cloud of Grondone form about noon, and keep together until four or five o'clock, and then, after a few claps, give way to a small thunder-storm."
"We find the following curious passage in a recent description of the caves and grottoes of Nor- way : " A promontory of the Lyse-Fiord contains a cavern really terrible, on account of the meteoro- logical phenomena of which it is the scene. It is well known that there are no rocky cliffs of more sinister aspect than those of the Lyse-Fiord. It is toward the fifty-ninth degree of latitude, at a short distance to the eastward of the port of Stavanger, that this arm of the sea opens. It is a prodigious ditch, twenty-five miles or so in length, shut in between two walls of sharp-pointed, perpendicular rocks of the average height of more than half a mile. No doubt the first mariner who navigated the still, black waters of this chasm, must have proceeded with a certain feeling of horror, asking himself at every turn if he was not about to see
132 METEOES AND METEOEIC PHENOMENA.
some frightful old Norse deity start up before him. Even now it is not without a shudder that one penetrates this sea-defile, in which the ancients would have recognized the entrance to Hades.
" When the southwest wind blows rudely, and plunges by violent gusts into the vast chasm of the Lyse-Fiord, a strange meteoric phenomenon adds to the terrible majesty of the scene. Fifteen hundred feet above the level of the sea, and at two-thirds of the height of the wall that rises to the southward of the entrance to the gulf, there is seen a flash of lightning leaping, from time to time, from the black rock, spreading, then con- tracting, then expanding, and shrinking again, and dispersing in luminous fringes before it reaches the northern wall. This broad tongue of fire advances, whirling round and round as it goes, and it is to this rotary movement that the apparent expansions and contractions of the light- ning are due. E-apid detonations are heard with an increasing power before the live flame leaps from the rock ; a violent clap of thunder accom- panies it, and reverberates in prolonged echoes through this narrow corridor of the sea. One would think that some battery, hidden behind the cliff, was cannonading some invisible casemate in the opposite wall."
EFFECT OF THUNDER-STORMS. 133
During volcanic eruptions, the clouds that issue from the craters emit numerous flashes of lightning. These clouds are composed of smoke and vapor, mingled with ashes, and often of ashes alone. In 1631, an immense column of smoke rose from Vesuvius, and was borne for a distance of more than one hundred and twenty miles. During its passage it threw off shafts of lightning, accompanied with thunder, that killed several persons. In another eruption, the cloud, which was extremely black and composed of impalpable ashes, got as far as the town of Tarentum, where the lightning set fire to a number of buildings. These volcanic thunder-storms have also taken place at sea. In 1811, when the island of Sabrina emerged from the waters in the vicinity of the Azores, the columns of dust and ashes that rose from it were furrowed with lightning of extraor- dinary vividness, according to the statement of the ship-captain who witnessed the phenomenon.
THE EFFECT OF THUNDER-STORMS ON SUBTERRANEAN WATERS.
Arago speaks of modifications that have some- times taken place in underground waters during stormy weather, in which thunder and lightning play a part ; of springs that become troubled and
134: METEORS AND METEORIC PHENOMENA.
overflow, even after a great drought ; of deep wells heard boiling and bubbling noisily ; of fountains leaping from the rock with sensibly augmented projectile force. Yallisneri has remarked that the salsae and solfatarae, or volcanic salt and sul- phur fields, in the vicinity of Modena, announce thunder-storms by a sort of ebullition, and by noises resembling thunder.
" Historians and meteorologists," says Arago, "mention local inundations the effects of which seemed to go far beyond what the small quantity of rain issuing from the clouds, and falling with- in a certain radius, could have led any one to fear." It has rarely happened that, upon such oc- casions, immense masses of water have not been seen rising from the bowels of the earth, for a greater or less period of time, from openings until then unknown, or that a violent thunder-storm has not been the precursor of the phenomenon and probably its most immediate cause. Such, for instance, were in every particular the circum- stances of the inundation that in July, 1688, almost utterly destroyed the villages of Kettlevel and Starbottom in Yorkshire, England. During the storm an immense chasm formed in the adj ac- cent mountain, and, according to eye-witnesses, the mass of water that gushed from it contrib-
EFFECT OF THTJNDER-STOKMS. 135
uted, as much as the rain, to the ravages that ensued.
In October, 1755, according to Beccaria, a sudden inundation produced great destruction in most of the valleys of Piedmont. The river Po overflowed, and the disaster was preceded by hor- rible thunder, orrendi tuoni, says the learned Ital- ian. Everybody agreed that the principal cause of the inundation was the immense volume of water which, during the storm, suddenly issued through new openings from underground among the mountains.
These local fractures of the solid crust of the globe would have nothing very extraordinary about them, were it proven that, in stormy weather, the water has a tendency to seek the clouds, and that this tendency manifests itself by abrupt outbursts from below. This is precisely the conclusion to be drawn from observations made on board the packet-ship New York in 182Y. While the storm raged around the vessel in question, the sea was in a continual ebullition of such a nature as to convey the idea of subter- ranean volcanoes. Especial note was taken of " three columns of water which leaped high into the air, then fell back, then leaped up again, and
once more subsided."
7
136 METEORS AND METEORIC PHENOMENA.
THE USEFULNESS OF THUNDER-STORMS.
Science teaches us to appreciate the beneficent effects of the thunder-storm, the appearance of which was once considered a sign of celestial dis- pleasure. The explosions of thunder and light- ning produce a profound modification in the con- stituent elements of the atmosphere. The gases, which are held merely in a state of simple mixture in the absence of the electric spark, are combined by its agency in such manner as to form ne"w sub- stances, that are detected in various quantities in rain-water. Under certain circumstances these new combinations deposit the nitre that is found on the surface of the soil in different countries. The agricultural efficacy of that substance has been known since the days of antiquity. Yirgil mentions it in his "G-eorgics." Agricultural writers recognize the value of other products of the thunder-storm in helping vegetation. Each electric discharge engenders in the atmosphere fruitful principles of life, which are drawn into the soil, where the roots of plants imbibe them, and so communicate a fresh glow to their foliage and flowers.
Thunder-storms, also, purify the atmosphere. The passage of the lightning gives oxygen more
THE USEFULNESS OF TIIUNDEK-STOKMS. 137
active properties, and transforms it into ozone. Although this gas is but little known, we are safe in attributing to it a very energetic agency in destroying miasma and neutralizing putridities that, in spreading throughout the atmosphere, render it unfit for respiration, and give rise to the severest maladies. Ozone may be produced in the laboratory by means of strong electric sparks. If a bell glass be filled with it, spoiled meat and of- fensive dirt placed under it soon lose their repul- sive odor. All the imperceptible remains of or- ganic substances are consumed on coming into contact with the electrified air, and M. Schoen- bein has established the fact that air, containing a very small proportion of ozone, will disinfect an equal volume of vitiated atmosphere.
According to recent researches, the hygienic conditions of several regions appear to be in rela- tion to the quantity of ozone in the atmosphere. In many observatories, this quantity is daily as- certained by means of the variations of color re- vealed by a chemical substance. It is probable that^irnportant laws will ultimately be developed from a larger collection of facts.
After a thunder-storm, a peculiar odor, usually spoken of as a smell of sulphur, or brimstone, is diffused through the atmosphere. This smell is
138 METEORS AND METEORIC PHENOMENA.
due to the presence of ozone, and, farther on, we shall see how it manifests itself in the haunts of the great electric meteors that serve the purpose of thunder-storms in the polar regions.
CHAPTER VI.
WHIRLWINDS.
Water-spouts.— Electric Whirlwinds.— Sand-storms.— Water-spouts at Sea.— Water-spouts on Land.— Tornadoes.— Cyclones.— Hurricanes.
WATER-SPOUTS.
" AMONG the great meteors that come to trou- ble the apparent order and harmony of Nature — among the grand phenomena which carry terror and desolation wherever they appear, there is one which distinguishes itself from the rest by the strange and gigantic forms it assumes, by the outside forces that it seems to obey, by the un- known and apparently contradictory laws that appear to regulate it, and, to sum up, by the dis- asters it occasions. These disasters themselves are accompanied by peculiar circumstances, so re- markable that the cause of them cannot be con- founded with that of other meteors baleful to humanity. This meteor, so extraordinary, so
140 METEORS AND METEORIC PHENOMENA.
menacing, and fortunately so rare in our lati- tudes, is the one designated by the general expres- sion of water-spout"
Such are the words of M. A. Peltier, in his " Observations and Experimental Researches on the Causes that concur in the Formation of Water-spouts."
The least violent and least dangerous whirl- winds are those that are produced by the meeting of contrary winds, and have no other cause than the mechanical impulsion of the forces set in mo- tion during great atmospheric disturbances. Such whirlwinds often form in mountainous countries, where the wind buries itself in the gorges, blows in varying directions, and is sometimes abruptly interrupted by obstacles that turn it aside.
" I have often witnessed these phenomena in the Alps," says Kaemtz, " but will content my- self with relating the following fact: A very strong south wind was blowing over the summit of the Righi, and the clouds that passed above my head were sweeping in the same direction. The north wind was blowing toward Zurich, and as- cending along the northern slope of the mountain. "When it reached the summit, light vapors formed and seemed to seek a passage over the crest, but, the south wind throwing them back, they ascended
WATEK-SPOUTS. 141
toward the north, at an angle of forty-five de- grees, and disappeared at the top. The struggle of these two contrary winds lasted several hours. A great number of whirlwinds formed at the point where the two winds met, and travellers, who usually feel but little interest in meteoric phe- nomena, were struck by this singular spectacle."
The terrible whirlwinds that are met with chiefly in the tropics, or accompany great thunder- storms, often spring up in the midst of a calm, and are probably produced by the most formidable forces of electricity. The clouds, according to Peltier, are the source of this power, when, after a rapid evaporation in calm, warm weather, they have retained the electricity that was in the va- pors, and that, most usually, is dispersed through the damp atmosphere into the soil. When the clouds, thus charged with electric fluid, and often accumulated in enormous masses, chance to com- bine their forces with the perturbations of the at- mosphere, they act with those that are peculiar to them, and add powerful influences of attraction and repulsion to the violent shocks of the air. All the observations that have been made relative to water-spouts, tend to prove that they are the result of a transformation of these electric clouds.
Before the appearance of these water-spouts,
142 METEOES AND METEORIC PHENOMENA.
which are much more frequent at sea than upon the land, black, stormy clouds collect, and the lowermost one in the series is seen descending in the shape of a reversed cone, the point of which approaches the ground or the water in a greater or less degree. Beneath this descending cloud, the waters appear to be in a state of ebullition, and the vapor that issues from them rises like smoke. On land, light bodies, such as dust, etc., are carried upward and form whirlwinds. Some- times the point of the cone touches the sea, and there hollows out a grand circular depression, as though a violent current of air issued from it. Less frequently, the waters are lifted up in the form of a column, or an ascending cone. In the midst of the vapor-clouds that surround the lower part of the water-spout, sheaves of water gush upward, and fall again on the outside. "This mass of water," says Peltier, " raised in the form of a whirling, boiling smoke ; these ascending and descending jets, seen from a distance, have the appearance of a thicket, or a hedge, such as Eng- lish navigators are accustomed to call e the bush.' J: "Water-spouts nearly always emit a deafening noise, a strange, whizzing sound, which increases or diminishes according to the greater or less dampness of the ground over which they pass.
ELECTRICAL WHIRLWINDS. 143
They are frequently accompanied by whirlwinds in the air, lightning, thunder, hail, and rain.
ELECTRICAL WHIRLWINDS. SAND-STORMS.
There have been dry, whirling storms, or whirlwinds, that have caused great destruction, without having been preceded by any gathering of opaque clouds. Peltier admits that the invisible vapors collect in transparent clouds that may be charged with electricity, like opaque clouds, and reproduce the same phenomena.
On the great deserts, during a dead calm, and under a blazing sun, the sand sometimes rises in the midst of electric whirlwinds, that remind one of a water-spout. Piddington, in his "Law of Storms," relates a very interesting summary of observations made in Hindostan by Dr. P. Bad- dely:
" My observations extended from the warm season of 1847, the period of my first coming to Lahore, until 1850 ; here is the result :
"Sand-storms are caused by spiral columns of electric fluid passing from the atmosphere to the ground. They have a forward movement, a rotary movement, like the whirling storms at sea, and a special spiral movement from top to bottom. It is probable that in an extensive sand-storm,
144: METEORS AMD METEORIC PHENOMENA.
most of these columns move together in the same direction, and that, while the tempest lasts, sudden and numerous gusts take place at in- tervals, in which the electric tension is at its maximum.
" The same phenomena are to be seen in every case of sand-storm ; from those that are but a few inches in diameter, to those that have fifty miles and more of extent, the phenomena are identical.
" It is a curious fact that some of the smallest sand-storms that are seen occasionally in the great arid plains of this country (India) and Af- ghanistan, above the Bolan Pass, and which are called ' devils ' in vulgar parlance, are stationary for a while, that is to say, for an hour or more, and, during all this time, the sand, or dust, and other light bodies from the ground, keep up their whirling movement in the air. In other cases, small sand-storms advance slowly, and when they are numerous they move usually in the same di- rection. Frequently, birds, such as kites and vul- tures, soar above these heights, and evidently follow the direction of the column, as though it gave them pleasure. I think that the phenomena associated with sand-storms are identical with those that are presented by water-spouts, in white squalls at sea, and in tornadoes of every descrip-
SAND-STOKMS. 14:5
tion ; and that they arise from the same cause, that is to say, from movable columns of electri- city.
" In 184Y, at Lahore, desirous of satisfying my mind in regard to the nature of sand-storms, I placed in the open air, on the roof of my house, a copper wire insulated upon a bamboo. I led one end of the wire into my room, and put it in com- munication with an electrometer with a golden plate and a wire connecting with the ground. A day or two afterward, during the passage of a small sand-storm, I had the pleasure of seeing the electric fluid passing from one wire to the other in vivid sparks, and powerfully affecting the elec- trometer. The fact was, henceforth, explained ; and since that time I have, by the same means, taken note of at least sixty sand-storms of differ- ent dimensions. All of them presented the same phenomena.
" I have observed that, usually, toward the termination of a storm of this kind, the rain falls suddenly, and that, instantaneously, the current of electricity ceases or greatly diminishes ; when it continues, it would seem that it does so only in cases where the storm is of considerable power, and lasts for some time afterward."
The author then gives an account of his ineth-
146 METEORS AND METEORIC PHENOMENA.
od of observing these phenomena, and afterward goes on with his description of whirlwinds :
" The sky is clear ; not a breath of air is stir- ring ; but see, presently there is a bank of clouds far down the horizon, and you are surprised that you did not notice them before : a few seconds go by, and the mass of cloud has covered half the celestial hemisphere ; there is no time to lose ; it is a sand-storm, and every one rushes hurriedly in-doors to escape being caught in it.
" The electric fluid continues to descend inces- santly along the conducting wire, while the storm lasts. The sparks are often more than an inch in length, and emit a dull, crackling sound. Its in- tensity varies with the force of the storm, and, as I said above, is strongest during the sudden gusts.
" One of these storms, which took place last year in the month of August, seemed to come .from the direction of Lica, on the Indus, to the west of Lahore. An officer on the march, twenty miles distant from Lica, was suddenly enveloped in it. His tent was swept away, and he was thrown down and nearly suffocated by the sand. At Lica the whirlwind cracked the walls of a solid brick building, in which the same officer had re- cently lodged, and tore up some trees in the en- virons by the roots.
WATER-SPOUTS AT SEA. 147
" I have repeatedly tried to discover the kind of electricity developed, and have found that it is not invariably the same. Sometimes it appears to be positive, and at others negative. It changes during the storms."
WATER-SPOUTS AT SEA.
The extraordinary effects produced by these tornadoes, their strange destructive power, and the singularity of their forms, prepare our minds to comprehend how they were regarded in old times as evil spirits, who, in this prodigious disguise, re- joiced in desolating the face of the country and spreading terror far and near. Superstition, even now, sometimes attributes a sort of personality to these destructive meteors, whose monstrous aspect and capricious movements vividly strike the im- agination. Then the latter, by the aid of ignorance, may give birth to the most absurd fantasies, hap- pily dispelled in our time with ease, by the light of science and reason.
Peltier has reproduced the following account of a whirlwind seen by Dr. Leymerie on the 2d of September, 1804, on board the Le VoMtour :
" This vessel was coming from Cayenne, steer- ing for the coast of Africa, and was not far from the river Gambia, when the whirlwind formed.
148 METEORS AND METEORIC PHENOMENA.
Before its appearance there was a dead calm. The preceding days had been very warm, and, since morning, the sky had become covered with heavy clouds. The cutter was in pursuit of a British slaver, when, all at once, those on board of her saw a column of water, about three hundred feet in height, rise from the sea to meet an- other column (of vapor), descending from the bed of clouds overhead. At this instant, the calm was broken and the storm began to rage furious- ly. The column in question was not composed of water in its liquid state, but in the condition of very dense vapor, as had been frequently re- marked. This column was luminous throughout its whole diameter, and had a slightly yellowish, or tawny, phosphorescent appearance. The sea itself was blazing with light, and the vessel left behind her a long wake of fire. The storm lasted for fourteen hours, and caused many disasters in those waters ! "
Navigators frequently have recourse to their guns, in order to break the water-spouts. "When the ball passes through them, they are sometimes seen to separate into two parts, which most usual- ly reunite very quickly. Sometimes, on the other hand, the ball simply dashes the water in jets on each side of the column, without affecting it other-
WHIRLWINDS ON LAND. 149
wise in the least. "Water-spouts, as Peltier re- marks, frequently offer a curious fact, which would seem irreconcilable with the theory of wind tornadoes being the cause of the phenome- non. Many cone-like points start from the clouds and soon combine in one and the same cylinder. It is difficult to demonstrate that different torna- does thus aggregate in a single shaft, while the attractive forces of electricity may readily enough determine this method of uniting. In the same manner, the cloudy cone is seen dividing into several spirals, which reunite and separate again, a circumstance that sets aside the idea of an impulsion received from the tornadoes of the air.
WUmLWINDS ON LAND.
Let us now reproduce two accounts of water- spouts on land, that will give an accurate idea of this terrible meteor. The first was observed and described by the learned meteorologist Professor Grossmann :
" On the 25th of June, 1829, about two o'clock in the afternoon, at a point a league below Treves, east-northeast of Ruwer and Pfalzel, about twenty degrees above the horizon, a phenomenon showed itself that struck a great number of men at work
150 METEORS AND METEORIC PHENOMENA.
out of doors with amazement, and kept them in uneasy suspense for half an hour.
" A fall of rain had taken place and the sky had remained covered with clouds, when, all at once, from the middle of a black cloud that rose in the east-northeast, a luminous mass began to move in the opposite direction and rend it violently. The cloud speedily assumed, at the top, the form of a chimney, from which escaped a whitish-gray smoke, mingled occasionally with jets of flame, and rising through several openings with as much force as though, to use the expression of the look- ers-on, it had been driven by so many bellows.
" The meteor had advanced over the vineyards of Disburg and opposite to Ruwer, when, some distance farther to the south, on the right bank of the Moselle, and completely in contact with the soil, another meteor suddenly appeared. It scat- tered the heaps of charcoal piled up around a tree, threw down a laborer at an adjacent lime- kiln, and dashed across the Moselle with a terrific concussion, as though a great many stones were shaken together. The water leaped in a column high into the air.
" Continuing to roll along with the same up- roar, the meteor, still grazing the ground, darted across the Pfalzel country, leaving everywhere be-
WHIEL WINDS ON LAND. 151
hind it the most evident traces of its zigzag route in the grain-fields and vegetable-patches. Part of the crops was totally destroyed, part was beaten down and torn to pieces, and part whirled away into the air.
" Many women fainted with terror as the me- teor passed near them, and others, who were far- ther off, hid themselves or fled, shrieking that the 6 fields were all on fire ! ' Two laborers, who had climbed a tree, watched the meteor along its en- tire course ; a third had even the bold idea to fol- low it, which it was easy to do, at the ordinary walking gait. At length, in one of its zigzag movements, it suddenly enveloped him. He felt himself at one moment violently jerked forward, at another tossed up. He then bent down, bracing himself strongly on the ground, with his working- tools ; but he was, nevertheless, prostrated. The tornado, however, left him, and passed on its way. The man could recollect no particular impression affecting his smell or taste, but merely a deafening noise. He affirms that there were two currents of air, the one rising obliquely, carrying up with it the stalks and stems of the grain, along with other light bodies, and the second operating in a con- trary direction.
" The track that the meteor had opened for it-
152 METEORS AND METEORIC PHENOMENA.
self across the country was, according to different statements, from ten to eighteen paces in breadth and about twenty-five hundred paces in length. Its shape was almost conical, and its color was, at one moment, a grayish-white or yellow, at an- other a dark-brown, but most of the time a fiery red. The first meteor remained in the air above the second, and followed a nearly parallel route, going toward the north. For about eighteen minutes it presented a large mass of whitish-gray cloud, which repeatedly seemed to vomit name- colored smoke, and, when seen at the distance of about a mile and a half, had the form of a serpent about one hundred and forty paces long, with its head to the north-northeast and its tail in the opposite quarter.
" In eight or ten minutes, the tail had already changed its position by bending downward. Just at the moment when it was about to touch the head, the whole phenomenon disappeared, and the lower meteor vanished at the same instant, without any detonation from either of them, as an eye-witness affirms ; but, with this, a strong smell of sulphur spread over the whole country. Near- ly at the same moment, a storm burst forth among the woods situated to the north-northwest of the place where the meteor had appeared, and was
THE TOENADO OF MONVILLE. 153
accompanied by a fall of extremely large hail- stones.
" The sun was not seen during the whole of this time, as most of the spectators declare, and there was not a breath of wind.
" The upper meteor was seen from Cassel, Gut- weiler, and other places, as also at Treves. It seemed to descend from the heights of Hoch- wald."
THE TOENADO OF MONVILLE.
The tornado of Monville and Malaunay pro- duced still more fearful effects. The description, incorporated in the Oomptes Rendus of the French Academy of Sciences, has been summed up by Professor Daguin, of Toulouse, as follows, in his " Treatise of Physics " :
" On the 19th of August, 1845, a violent south wind prevailed in the environs of Rouen. In the afternoon, a gust from the southwest, driving some very dark clouds before it, met the southern current, and formed a strong whirlwind, with a sidelong movement that tore up a hundred and eighty bulky trees, twisting and wrenching nearly all of them, and throwing down a drying-house belonging to an adjacent factory. At the same mo- ment, there was a heavy shower accompanied with
154: METEORS AND METEORIC PHENOMENA.
thunder and hail. However, there was no tornado as yet, properly speaking ; but, after receding to a distance and traversing some twenty-five miles, the storm suddenly returned into the valley near Malaunay and Monville, passing through a wood, the trees in which it broke off close to the ground. At that moment, an enormous cone, of sharply-de- fined outline and as black as coal-smoke, was seen to assume shape. The top of it was of a reddish-yel- low, while it emitted flashes of lightning and a heavy rumbling sound. In a few seconds, the tor- nado hurled itself, with appalling velocity and by zizag motion, through three considerable spin- ning-mills in succession, crushing them and all the working-people in them. The roofs were swept off, and not one stone left on another. The looms were twisted, the heavy pieces shattered, chiefly, too, where there were ponderous masses of metal. The trees in the vicinity were flung down in ev- ery direction, riven and dried up for a length of from six to twenty feet and more. While clear- ing away the ruins, in the attempt to rescue the unfortunate people buried beneath them, it was noticed that the bricks were burning hot. Planks were found completely charred, and cotton burned and scorched, and many pieces of iron and steel were magnetized. Some of the corpses showed
THE TOKNADO OF MONVTLLE. 155
traces of burning, and others had no visible cuts or contusions, but seemed to have been killed by lightning. Workmen who were hurled into the surrounding fields, all agreed in saying that they had seen vivid flashes and had noticed a strong smell of sulphur. Persons who happened to be on the adjacent heights, alleged that they saw the factories wrapped in flames and smoke as the cloud enveloped it. The breadth of the belt laid waste by the tornado was seven hundred and fifteen feet on the level of Malaunay, less than one and a half miles from the point where its ravages began, nine hundred and ninety-five feet in the middle, and one hundred and ninety-five feet near Cleres, where the cloud disappeared. The length of the belt, as the bird flies, was about ten miles. " One really very remarkable circumstance is, that debris of all kinds, such as slate, glass, planking, and pieces of wood- work, mingled with cotton, fell near Dieppe, at a distance of from fifteen to twenty-three miles from the scene of the catastrophe. These various objects were beheld in the air by several persons, who mistook them for the leaves of trees, so high were they above the ground. Among the scattered fragments carried thus far, was a scantling more than a yard long, five inches wide, and half an inch thick.
156 METEORS AND METEORIC PHENOMENA.
Happily, all such whirlwinds are not so destructive as the one described."
When a thunder-storm changes to a whirlwind, the sound of the thunder ceases at once. The electric discharges are effected through the de- pressed clouds, and the trees that stand in the track of the meteor. These trees, when traversed bj the electricity, are dried up in a moment, and the whirl breaks them instead of tearing them up. The enormous meteor of this kind that laid waste the parish of Chatenay, on the 18th of June, 1839, in this way destroyed the plantations of trees in the valley lying "between the hills of Ecouen and the eminence of Chatenay. "Fifteen hundred feet of trees," says Peltier, " had evidently served as conductors to masses of electricity, and to con- tinual, incessant discharges of lightning. The temperature, greatly increased by this flow of the electric fluid, instantaneously vaporized all the moisture in these vegetating conductors, and this vaporization caused every one of them to split lengthwise."
TORNADOES PROPER.
The hurricane - storms^ or cy clones , during which the wind blows with extraordinary violence, veering at a leap, more or less suddenly, from one
TORNADOES PROPER. 157
point of the horizon to the other, are also classed among those terrific phenomena, the whirling motion of which seems ascribable to an immense electric action. All the descriptions that have been given of them go to show that these meteors are produced like those last described — Toy beds of thunder-clouds.
The tornadoes of the western coast of Africa are sometimes rectilinear gales of wind, like the pamperos of South America, and the arched squalls of the straits of Malacca, " which rise," says Horsburgh, in his " East India Sailing Direc- tions," " with a black arch of clouds ascending rapidly from the horizon to the zenith, and scarcely giving time to take in sail." But, in most cases, these tornadoes are veritable " cy- clones in miniature," as Piddington correctly calls them.
" On the approach of a tornado," says Hop- kins, in his work on atmospheric disturbances, " a dense mass of clouds gathers in the east and on the horizon ; it is accompanied by frequent, dull, but brief noises, that remind one of the growling of some wild animal. This bank of clouds gradually covers a part of the horizon, and extends from there to the zenith ; but generally, beforehand, a
small, radiating arch, of well-defined outline, ap- 8
158 METEOES AND METEORIC PHENOMENA.
pears on the edge of the horizon, and continually increases. Long before it reaches the ship, one hears the whizzing of the wind, which produces nearly as much noise as the roaring of the thunder when it seems to rend the clouds apart with vio- lence. The course of the gale is distinctly marked by the line of foam that it raises."
The following description, given by Mr. Min- graden in the Quarterly Journal of Science, 1837, completes these observations : " When the torna- do is approaching, it is remarked that the rain seethes down in torrents, and that the flashes of lightning part the clouds in such profusion that they resemble continual discharges of electric fluid. When, however, the squall has got within half a mile of the ship, these electric appearances cease altogether. The rain only continues the same. When the tornado passes over the vessel, there is a dull crackling distinctly heard in the rigging. It is occasioned by the descent of the electric fluid along the masts, the tips of which serve to attract it ; and I have been told that, when this phenomenon occurs at night, every part of the rigging seems illuminated. When the squall has passed the vessel about half a mile, the same signs that characterized its approach from the land reappear exactly, and before attaining the
TORNADOES PROPER. 159
same distance from the ship. The lightnings again descend in continuous sheets, and in such abundance that they resemble the torrents of rain that accompanied the squall. These squalls occur every day during a certain part of the year termed the harmattan 1 season. The jet of black clouds, coming from the mountains, begins to appear about nine o'clock in the morning, and reaches the sea about two o'clock in the afternoon. Another singular fact follows these tornadoes. After having whirled over an extent of eight or nine leagues, they disappear, and flashes of light- ning are beheld darting up from the sea. The vio- lence of the wind during the storm is excessive.
" The circular motion of the air at the outset of these tornadoes is indicated by the whirling about of the leaves and straws that are caught up by it. These meteors precede the rainy season, and are more or less violent, according to the state of the atmosphere. Ordinarily, they last but a little while, and are always followed by a heavy shower, which revives vegetation, and freshens the atmos- phere, that had been made stifling by the blazing heat. Hence, every one feels a vivifying sensation of enjoyment after they are over."
1 The harmattan is a dry wind that blows from the interior of Africa toward the Atlantic, principally in the months of Decem- ber, January, and February.
160 METEORS AND METEORIC PHENOMENA. CYCLONES. HURRICANES.
Piddington relates the meeting of two torna- does, which, in violence, could be compared to cyclones. The phenomenon was observed at Charleston, in South Carolina, May 2, 1Y61, at two o'clock in the afternoon :
" The tornado crossed the Ashley River, and swooped down upon the shipping at Rebellion Wharf, with such fury as to threaten the destruc- tion of the entire fleet. From the city it was seen coming at first rapidly toward Wappo Creek, like a column of smoke, with a very irregular and tumultuous movement. The quantity of vapor that composed this column, and its prodigious velocity, produced so intense a commotion that it agitated Ashley River to its depths, and left the channel bare. The ebb and flow made the ship- ping float off to a great distance. "When it struck the river, it made a noise like continuous thunder ; its diameter, at that moment, was estimated at fif- teen hundred feet, and its height, as seen from Charleston, at twenty-five degrees. It was met, at White Point, by another whirlwind, which descend- ed Cooper River, but was not equal to the first. When they came together, the commotion in the air was much greater still; the foam and the
CYCLONES. 161
vapor seemed to be thrown to the height of forty degrees, while the clouds, that hurried from all directions toward that point, seemed to rush thither and whirl about, at one and the same time, with incredible velocity. The meteor then darted upon the shipping in the roadstead, and reached them in three minutes, although the distance was nearly six miles. Out of forty-five vessels, five were sunk on the spot ; the State ship Dolphin and eleven others were dismasted. The damage, estimated at more than £200,000, was done in a moment, and even the vessels that sank were swallowed up so rapidly that the people who were below had scarcely time to scramble up on deck. The whirlwind of Cooper River changed the course of the one that came from Wappo Creek, which, had it not been for that, would, pro- ceeding in the same direction, have swept away the city of Charleston before it like so much straw.
"This terrible column was first perceived about noon, at more than fifty miles west-south- west of the roads. It destroyed every thing in its way, making a complete avenue when it passed through the woods. The loss of the five ships was so sudden that it is not known whether it was the weight of the column of wind, or the
162 METEOKS AND METEOEIO PHENOMENA.
mass of water driven upon them, that made them go down."
It is near the Antilles, in the Gulf of Mexico, and in the Indian Seas, that the most disastrous hurricanes burst forth. These are the appalling cyclones, during which Nature seems to return to original chaos.
" Sometimes," says an old author, quoted in the article on " ^Eolian Researches " in the Nauti- cal Magazine for 1841, " sometimes, toward that side of the horizon from which the storm comes, is first seen something like a cloud blazing in the most astonishing manner ; and some of these hur- ricanes and whirlwinds have appeared so terrific as to convey the idea that the entire atmosphere and sea were in one tremendous blaze. Captain Prowd, of Stepney, in one of his voyages to the East Indies, encountered a storm of this kind, and left some particulars concerning it, which I have extracted from his journal. The sea was agitated throughout, and what was the most astonishing and terrifying circumstance was, that the sky be- came surprisingly red and inflamed on the north- ern part of the horizon. The sun was then at the zenith. Signs of a tempest were recognized in these appearances, and the storm came, as had been foreseen. As the darkness grew thicker, the
HURRICANES. 163
violence of the wind increased until it attained the proportions of an awful hurricane. At one o'clock in the morning it beat with such force that it was impossible to keep a sail on the vessel. Seven men could scarcely steer. The whole at- mosphere, the sky, and the sea, in their wrath, seemed but one mass of fire."
An official account of the fearful hurricane that devastated Guadeloupe on the 25th of July, 1825, contains the following passage :
" The wind at the moment of its greatest in- tensity seemed luminous ; a silvery flame streamed through the chinks in the walls, the key-holes, and other openings, and made one think, in the dark- ness inside of the houses, that the heavens were on fire."
Sometimes, a dense bank of clouds of mena- cing blackness is seen on the side of the horizor from which the cyclone comes. Sheets of light ning issue from it, the " terrible magnificence * of which, according to Piddington, recalls the splendors of the aurora borealis. At the same time, the sea becomes covered with phosphores- cent coruscations that fill the sombre night with a pale radiance; while, during the daytime, a blood-red sky spreads its sinister hue over the whole horizon. A profound calm nearly always
164 METEORS AND METEORIC PHENOMENA.
precedes the hurricane, which is also announced by " the distant moaning of the elements, as though the winds were engulfing themselves in a vault. These remote rumblings recall the sound of a thunder-storm heard in caverns."
The sea assumes a murky color, breaks foam- ing on the shore, and lifts itself sometimes in enormous tidal-waves ( " the heavings of the tem- pest " ), produced by the approach of the cyclone. The elevation of the usual level of the waters, which is almost always the sign of violent storms or heavy rains, often causes inundations of low shores beaten by the hurricane.
The diameter of this immense meteor varies from fifty to one hundred miles, and sometimes more. The disk of whirling air has probably never more than from one to ten miles of vertical height. Placed upon a summit, like the Peak of TenerifFe, the observer would see it pass below him, as travellers among the Alps often view thunder-storms devastating the valleys at their feet. In most of these cases, the disk of the cyclone is so thin that the sky can be distinctly seen through the black masses of cloud. Pidding- ton quotes the following extracts from the log of two sea-captains :
"We observed one very remarkable circum-
HUKKICAJSES. 165
stance : while, all around the horizon, there ap- peared a bank of dense clouds, the sky at the zenith was so perfectly clear that we could see the stars ; and every one on board noticed above the mizzen-mast-head a meteoric light of peculiar brightness.
" While we were lying-to, the clouds were rent asunder, and the sun, gleaming over the whole surface of the water, gave the foam a tinge as white as snow, and then as richly colored as the rainbow in all its shadings."
Numerous observations tend to prove that the disk of the storm is nearly always inclined for- ward. While the front of the hurricane is at- tacking the land or the sea, the rear rises, and shows long trains of clouds, which are seen whirl- ing about in the most extraordinary manner. Strong discharges of electricity take place at the same moment and announce the termination of the cyclone.
The typhoons of the India Ocean are preceded by the same signs, and accompanied by the same phenomena, as the cyclones of the Atlantic, from which they differ in some unimportant particu- lars only. In the China seas, the strongest of these hurricanes are termed " iron whirlwinds."
The frightful sea that they heave up ; the
166 METEORS AND METEORIC PHENOMENA.
tremendous violence of the wind, blowing in op- posite directions from one side to the other of the disk ; the dangerous calm that reigns at the cen- tre, and leaves the ship motionless under the shock of monstrous billows ; the cataracts of rain ; the terrific din of the elements, — all unite to render the struggle hopeless for the seaman. It is es- pecially at night, in the midst of profound dark- ness, under the livid lightnings, or in the strange phosphorescent glare which sometimes envelops the ship, that the horror of the spectacle defies description. " If the winds are let loose in a tempest," says Thomas Fuller, an old seaman, "they become raging madmen in a hurricane." In his voyage to the Isle of France, Bernardin de Saint-Pierre gives a very exact description of a hurricane that he witnessed :
" On the 23d of December, in the morning, the wind being at the southwest, the weather be- gan to work up for a gale. Clouds accumulated on the summit of the mountains. They were dark, olive, and copper colored. One long upper band that remained motionless was noticed. The clouds lower down were in swift motion. The sea broke with a great noise on the reefs. Many marine birds sought refuge on land and came fly- ing in from the open expanse. The domestic ani-
HURRICANES. 167
mals seemed uneasy. The air was heavy and warm, although the wind had not fallen. In view of all these signs that foretold a hurricane, everybody hastened to prop and brace his dwell- ing and carefully to close all the openings.
"About ten o'clock in the evening the tempest came on. First, there were fearful gusts, followed by moments of appalling calm, in which the wind seemed to recruit its strength. Thus it continued with augmenting violence during the night. My cottage having been badly shaken, I moved to an- other shelter. My hostess was in tears for fear that her house would be destroyed. No one went to bed. Toward morning, the wind having be- come still more violent, I saw that a whole front of the surrounding palisade was about to fall, and that a portion of our roof was lifting at one cor- ner. So, with some boards and rope, I prevented the damage. In crossing the yard to give some orders, I several times expected to be thrown clown. I could see walls falling in the dis- tance, and fragments of ruin carried away, as though they were cards. Rain fell at eight o'clock in the morning, but the wind did not cease. It was driven horizontally with so much violence, that it entered in jets at the smallest orifices.
168 METEOKS AOT) METEORIC PHENOMENA.
" At eleven o'clock, the rain fell in torrents. The wind subsided a little, and in ravines of the mountains on all sides prodigious cascades were formed. Pieces of rock detached themselves, and fell with a noise like that of a cannon, and as they rolled down they forced great gaps in the woods. The streamlets overflowed in the plain, which was like a sea.
" At one in the afternoon, the wind leaped round to the northwest, and drove the foam of the sea in huge clouds upon the land. It threw the vessels in port upon the shore, and they kept firing guns of distress, but it was impossible to help them. By those new concussions the houses were shaken in another direction and with nearly equal violence. The winds then made the com- plete round of the horizon, as is usually the case, and, after that, every thing became quiet again.
" A great many trees were blown down and bridges carried away. Not a leaf was left in the gardens, and even the grass, that strong, coarse, tropical herbage, appeared in some places to have been shaved off close to the ground."
Although these terrible meteors are chiefly frequent in the torrid zone, they also appear some- times in our temperate climates, on the Atlantic and Mediterranean coasts. We shall presently
HURKICANES. 169
see how our meteorological observations can fol- low them in their course, and warn the places menaced by them in good time.
" These convulsions of Nature," says Peltier, "seem necessary to reestablish the equilibrium of the atmosphere, and often, notwithstanding the terrors that they inspire, the inhabitants of the countries that they ravage invoke them with all their hearts.
" Dense, stagnant fogs, that cause disease, are dispersed by the storm ; abundant rains reani- mate life and spread freshness on all sides ; the air becomes pure and light ; renewed by the electric action of these tempests, it restores vigor to men and animals, exhausted by the overwhelm- ing heat of the burning season, and gives back their brilliant verdure to the wilting plants. To the commotion of the hurricane, the howling tem- pest, the torrents of rain, the lightning, and the thunder, succeed the serenity of the fine weather, the calm, the pure light, and the beauty of an in- comparable spring."
CHAPTER VII.
RAINBOWS.— CROWNS AND HALOS.
Description of the Rainbow.— Play of Light in the Drops of Water.— Varied Appearances of the Arch.— Supplementary Arcs.— The Cir- cles of Ulloa.— Crowns.— Colored Arcs.— Parhelia.— White Arcs. — Anthelia.— The Halo of Clere*.
DESCRIPTION" OF THE RAINBOW.
" 0 Thou, Light, eternally one ! dwell there, on high, with the Being eternally one! Thou, 0 changing Color! descend in friendly guise to man ! " — SCHILLER.
]STo scene that Nature presents, better symbol- izes this fine thought of the poet than the mag- nificent arch, painted by the sun upon the dark clouds of a retiring tempest. In all ages, the rainbow has charmed the imaginations and awak- ened a feeling of hope and consolation in the minds of men. The Hebrew, impressed with the remembrance of the former floods that came upon the earth, felt his soul, that had been disquieted by the thought, resume all its serenity as he beheld
mimm. ,,...... :
DESCRIPTION OF THE RAINBOW. 171
the bow of promise. For Mm it was the token of Jehovah's pardon.
The gay fancy of the Greeks made the rain- bow the presage of happy tidings to the earth, the goddess Iris, the messenger of Olympus, ac- cording to their creed, left her transparent scarf floating on the clouds.
Ingenious fiction vanished at the approach of science, and the explanation of the rainbow is, to-day, one of the most complete parts we have of the physical theory of light. It is to Kepler, whose genius was prolific in so many directions, that we are indebted for the discovery of the first causes of the phenomenon ; he put it on record, although very briefly, in a letter written by him in 1601. Newton studied these causes with all the rigor of geometrical calculation, and was enabled to render an account of all the different modifications observed in the rainbow. After having calculated its dimensions, he verified the correctness of his observations by actual experi- ment.
"We never see the rainbow excepting when standing with our backs toward the sun, the space in front being traversed by a shower of rain, a cas- cade, or a simple jet of water. When the sea is agitated by a violent wind, and the sun's rays strike
172 METEORS AND METEORIC PHENOMENA.
the spray of the billows, rainbow curves and arcs are often produced upon it.
Usually, the phenomenon consists of two con- centric arches, with a considerable interval between them. The centre of these, as it is easy to prove, corresponds with that point in the heavens where the shadow of the observer's head would fall. The interior curve, which is the oftenest seen, pre- sents a series of prismatic radiations, arranged in such wise that the violet falls inside, and the red upon the outside. In the external curve, the colors of which are much weaker, the order of the series is reversed. Sometimes three bows are seen, but this occurs very rarely. The third, of an extreme- ly pale hue, then presents colors arranged in the same order as in the first instance.
The dimensions of these bows depend upon the height of the sun above the horizon. It must be close to the latter, in order to enable the ob- server, standing on the surface of the ground, to see arcs, or bows, embracing a half-circumference. It is only from the summits of mountains, or from a balloon high up in the air, that complete circles are visible, unless, as they frequently do, they appear in the spray of great waterfalls. A grand spectacle of this nature is enjoyed in contemplating the mag- nificent cascade of the Reichenbach. When we
WATERFALL RAINBOWS.
p. 173.
THE PLAY OF LIGHT IN DROPS OF WATER. 1Y3
saw it, the sun was rising, and the brilliant aerial coronce, or crowns, were floating above the chasm into which the waters plunged. Immense arches of the same kind form upon the white mist that rises over Niagara Falls.
The light of the moon also produces rainbows, but the yellowish reflection that it spreads over all the colors contrasts unfavorably with the vivid hues of the solar bows. The principal arch can- not be seen, and it is difiicult to distinguish the variation of the prismatic rays. During a storm which we witnessed on the open sea, we saw a luminous column of the strangest appearance de- scend from the sky. The ship's crew were struck with terror, and yet the meteor was entirely harm- less. The full moon was rising, tinged with red, at that moment, and the column of fire was but a fragment of a rainbow that it reflected on a sheet of rain.
THE PLAY OF LIGHT IN DROPS OF WATEE.
All the appearances of the phenomenon