It is convenient to place an indefinite title at the head of this article, in order to notice various classes of independent phenomena which immediately address themselves to the eye; and which are either plain developments of electrical action, or simply atmospheric meteors, or appearances resulting from its reflecting and refractive properties, or of obscure origin, but manifested in the atmosphere. To the former class the lightning belongs, beautifully playing among the distant clouds, or flashing with blinding glare and tremendous effect near the surface of the earth, warning man and beast of the presence of an agency able to extinguish animal and vegetable life in a moment, and utterly inappreciable in its swiftness, subtility and power. At the close of a hot, sultry day, over a level country, the igneous meteor often exhibits itself, in rapidly succeeding, broad, noiseless, and imposing sheets of flame, lighting up the whole range of the horizon, revealing for the moment the contour of the distant landscape upon which the shadows of the night have gathered, and discovering the outline of the clouds in the dusky sky. These displays, however startling to “the poor Indian, whose untutored mind” is alarmed at the slightest deviation from the ordinary aspect of things, are always harmless, and invite by their innocuousness and fascination the cultivated races to watch the bounding coruscations of the elastic element, besides contributing to render the fields of corn ripe unto the harvest. But it is otherwise when heat has overcharged the atmosphere with vapors, becoming piled into clouds of gigantic dimensions and massive architecture, which are often propelled by antagonist currents, and in different electrical conditions. After an unusual calm of nature, oppressive to the animal system, during which not a movement of the air is perceptible, and the leaves hang motionless upon the trees, while the brute creation indicate some intelligence of an impending change by their restlessness, an explosion commences. The flash is seen, the thunder heard, and the clouds open their watery store-house, a few distant and heavy drops increasing into a cataract of rain. Flash rapidly follows flash, and the interval between each appearance and the accompanying thunder peal becomes less. The pale hue of the lightning is exchanged for a vivid glare, in which a deep yellow, red, or blue is the predominant color, a variety of aberrations marking its course, the zigzag form showing that the fearful agent is near terrestrial objects. In this manner, “the detraction that wasteth at noonday” is frequently exhibited, now striking man and beast to the earth, or rending asunder the mighty oak of the forest, or firing the vessel of the hapless seaman, or shivering “the cloud-capt towers and gorgeous palaces,” the fanes of religion and the fortresses of war. Man has then a solemn sense of his helplessness and danger; and almost every creature sympathizes with him. The eel is restless in his muddy bed—the horse trembles beneath his rider—the cattle gather lowing to a covert—the eagle nestles in the cleft of the rock with folded wings—the hart looks wild and anxious: only the poor seal seems to experience agreeable sensations, for he will come out of his hiding-place in the deep, at the call of the thunder, and repose upon some overhanging ledge, as if calmly enjoying the convulsion of the elements.

Since the month of June 1752, when Franklin performed the celebrated kite experiment, by which he became the modern Prometheus, bringing down the celestial fire to the earth, the identity of lightning and electricity has been universally known. The theory of the electric fluid, as it is called, is to be sought for in philosophical treatises, our province being to notice its distribution, phenomena, and effects. That subtle principle which the Greeks denominated electricity, from elektron, amber, because the property was first noticed in that substance, appears to be a universally diffused agent, its presence having been detected in connection with the clouds, with hail, rain and snow, with vegetation, animals, and the interior strata of the earth. But undue accumulation transpires—the electrical equilibrium is disturbed; and the resulting phenomena of equalization are lightning and thunder. Thus two clouds, or a cloud and the earth, unequally electrified, tend to return to a condition of equality through a conducting medium, a metallic or moist body having the preference as a conductor, the discharge of electricity appearing in the form of a spark or flash, accompanied by a loud detonation according to its violence, the peal rebounding in echoes from cloud to cloud, and from hill to hill. Some regions of the globe are peculiarly subject to accumulations of electricity. Mr. Hamilton, in his work on Asia Minor, observes—“One of the most remarkable phenomena which I observed in Angora, was the great degree of electricity which seemed to pervade every thing. I observed it particularly in silk handkerchiefs, linen and woollen stuffs. At times, when I went to bed in the dark, the sparks which were emitted from the blanket gave it the appearance of a sheet of fire; when I took up a silk handkerchief, the crackling noise would resemble that of breaking a handful of dried leaves or grass; and on one or two occasions I clearly felt my hands and fingers tingle from the electric fluid. I could only attribute it to the extreme dryness of the atmosphere, and momentary friction. I did not observe that it was at all influenced by wind; the phenomena were the same, whether by night or by day, in wind or calm. Not a cloud was visible during the whole of my stay.”

Similar striking indications of the prevalence of electric action have frequently been observed by travelers when near the summits of high mountains, as by Sir W. J. Hooker on Ben Nevis, Saussure on Mont Blanc, and Tupper on Mount Etna. The latter, descending a field of snow, a good conductor, felt a slight shock upon entering a cloud which seemed electric, with a sensation of pain in the back. The hair of his head stood erect, and upon moving the hand near the head, a humming sound proceeded from it, which arose from a succession of sparks. Though a situation of great danger, yet we have several instances of such clouds having been traversed with impunity, when in the act of electrical explosion. The AbbÉ Richard, in August 1778, passed through a thunder-cloud on the small mountain called Boyer, between Chalons and Tournus. Before he entered the cloud, the thunder sounded, as it is wont to do, with a prolonged reverberation; but when enveloped in it, only single peals were heard, with intervals of silence, without any roll; and after he had passed above the cloud, it reverberated as before, and the lightning flashed. The sister of M. Arago was a party to a similar occurrence between Estagel and Limoux, and some officers of engineers likewise, during a trigonometrical survey on the Pyrenees.

The energy of atmospheric electricity appears to decrease as we recede from the equator to the poles, thus sympathizing with light and heat; for it is in tropical countries that the most terrific flashes of lightning and the loudest bursts of heaven’s artillery occur. Awful as these manifestations are occasionally in our temperate climate, they are but as a skirmishing of outposts to the general engagement of armies, when compared with inter-tropical displays. In Hindustan, in the Indian Ocean, along the African coast off Cape St. Verde, and in Central America, there is often a scene exhibited, which seems a rehearsal of the day “when the heavens being on fire shall pass away with a great noise.” Humboldt, during his residence at Cumana, witnessed a coincident development of electrical action, peculiar atmospheric phenomena, and terrestrial disturbance, during what is called the winter of that region. From the 10th of October to the 3d of November, a reddish vapor rose in the evening, and in a few minutes covered the sky. The hygrometer gave no indication of humidity; the diurnal heat was from 82·4° to 89·6°. The vapor disappeared occasionally in the middle of the night, when brilliantly white clouds formed in the zenith, extending toward the horizon. They were sometimes so transparent that they did not conceal stars even of the fourth magnitude, and the lunar spots were clearly distinguishable through the veil. The clouds were arranged in masses at equal distances, and seemed to be at a prodigious elevation. From the 28th of October to the 3d of November, the fog was thicker than it had been before; and the heat at night was stifling, though the thermometer indicated only 78·8°. There was no evening breeze. The sky appeared as if on fire, and the ground was every where cracked and dusty. About two o’clock in the afternoon of November 4th, large clouds of extraordinary blackness enveloped the mountains of the Brigantine and Tataraqual, extending gradually to the zenith. About four, thunder was heard overhead, but at an immense height, and with a dull and often interrupted sound. At the moment of the strongest electric explosion, two shocks of an earthquake, separated by an interval of fifteen seconds, were felt. The people in the streets filled the air with their cries. Boupland, who was examining plants, was nearly thrown upon the floor, and Humboldt, who was lying in his hammock, felt the concussion strongly. A few minutes before the first, there was a violent gust of wind followed by large drops of rain. The sky remained cloudy, and the blast was succeeded by a dead calm, which continued all night. The sunset was a scene of great magnificence. The dark atmospheric shroud was rent asunder close to the horizon, and the sun appeared at 12° of altitude on an indigo ground, his disc enormously enlarged and distorted. The clouds were gilded on the edges, and bundles of rays reflecting the most brilliant prismatic colors extended over the heavens. About nine in the evening there was a third shock, which, though much slighter, was evidently attended with a subterranean noise. In the night between the 3d and 4th of November, the red vapor before mentioned had been so thick, that the place of the moon could only be distinguished by a beautiful halo 20° in diameter. The vapor ceased to appear on the 7th; the atmosphere then assumed its former purity; and the night of the 11th was cool and extremely lovely. This account, with similar details from other observers, seems to indicate a more intimate relation than is generally admitted between the interior of the earth and its external atmosphere.

Among the regions peculiarly subject to electric phenomena is the country around the estuary of the Rio Plata. In the year 1793, one of the most destructive thunder-storms perhaps on record, happened at Buenos Ayres, when thirty-seven places in the city were struck by the lightning, and nineteen of the inhabitants killed. It is an observation of Mr. Darwin, founded on statements in books of travels, that thunder-storms are very common near the mouths of great rivers; and he conjectures that this may arise from the mixture of large bodies of fresh and salt water disturbing the electrical equilibrium. “Even,” he remarks, “during our occasional visit to this part of South America, we heard of a ship, two churches and a house, having been struck. Both the church and the house I saw shortly afterward. Some of the effects were curious: the paper, for nearly a foot on each side of the line where the bell-wires had run, was blackened. The metal had been fused, and although the room was about fifteen feet high, the globules, dropping on the chairs and furniture, had drilled in them a chain of minute holes. A part of the wall was shattered as if by gunpowder, and the fragments had been blown off with force sufficient to indent the wall on the opposite side of the room. The frame of a looking-glass was blackened; the gilding must have been volatilized, for a smelling-bottle, which stood on the chimney-piece, was coated with bright metallic particles, which adhered as firmly as if they had been enameled.” Near the shores of the Rio Plata, in a broad band of sand hillocks, he found those singular specimens of electric architecture, a group of vitrified siliceous tubes, formed by the lightning striking into loose sand. These tubes had a glossy surface, and were about two inches in circumference, the thickness of the wall of each tube varying from the twentieth to the thirtieth part of an inch. Four sets were noticed, probably not produced by successive distinct charges, but by the lightning dividing itself into separate branches before entering the ground. Similar cylindrical formations have been noticed in other places. Dr. Priestley has described, in the Philosophical Transactions, some siliceous tubes, which were found in digging into the ground, under a tree, where a man had been killed by lightning; and at Drigg, in Cumberland, three were observed within an area of fifteen yards, one of which was traced to a depth of not less than thirty feet. In the temperate climates electrical phenomena are most common, and usually most energetic in the summer season, and the displays are grander and more formidable in mountainous than in level countries. As we approach the poles, they become less striking; thunder is rarely heard in high northern latitudes, and only as a feeble detonation; and though lightning is more common, it is seldom destructive. In Iceland, in the winter, it often plays in the impressive but harmless manner which the natives call laptelltur. This is a fluctuating appearance of the whole sky, as if on fire, accompanied by a strong wind and drifting snow, but inflicting no further damage than that arising from the terrified cattle falling over the rocks in their efforts to escape from the phenomenon.

The rapidity of lightning, as measured by means of the camera lucida, M. Halvig estimates at probably eight or ten miles in a second, or about forty times greater velocity than that of sound; and according to M. Gay-Lussac, a flash sometimes darts more than three miles at once in a straight direction. M. Arago distinguishes three classes of lightning: First, luminous discharges characterized by a long streak of light, very thin, and well defined at the edges, of a white, violet, or purple hue, moving in a straight line, or deviating into a zigzag track, frequently dividing into two or more streams in striking terrestrial objects, but invariably proceeding from a single point. Secondly, he notices expanded flashes spreading over a vast surface without having any apparent depth, of a red, blue, or violet color, not so active as the former class, and generally confined to the edges of the clouds from which they appear to proceed. Thirdly, he mentions concentrated masses of light, which he terms globular lightning, which seem to occupy time, to endure for several seconds, and to have a progressive motion. Mr. Hearder of Plymouth describes a discharge of lightning of this kind on the Dartmouth hills, very near to him. Several vivid flashes had occurred before the mass of clouds approached the hill on which he was standing; and before he had time to retreat from his dangerous position, a tremendous crash and explosion burst close to him. The spark had the appearance of a nucleus of intensely ignited matter, followed by a flood of light. It struck the path near him, and dashed with fearful brilliancy down its whole length to a rivulet at the foot of the hill, where it terminated. Analogous to the discharges described as globular lightning are the fire-balls so often noticed, about which there has been no little scepticism; but the evidence cannot reasonably be doubted, that displays of electrical light have repeatedly occurred, conveying the impression of balls of fire to the observer. An instance is given by Mr. Chalmers while on board the Montague, of seventy-four guns, bearing the flag of Admiral Chambers. In the account read to the Royal Society, he states, that “on November 4th, 1749, while taking an observation on the quarter-deck, one of the quarter-masters requested him to look to windward, upon which he observed a large ball of blue fire rolling along on the surface of the water, as large as a mill-stone, at about three miles distance. Before they could raise the main-tack, the ball had reached within forty yards of the main-chains, when it rose perpendicularly with a fearful explosion, and shattered the main-topmast to pieces.” In an account of the fatal effects of lightning in June 1826, on the Malvern Hills, when two ladies were struck dead, it is stated, that the electric discharge appeared as a mass of fire rolling along the hill toward the building in which the party had taken shelter.

Mr. Snow Harris remarks upon the difficulty of explaining these appearances on the principles applicable to the ordinary electric spark. The amazing rapidity of the latter, and the momentary duration of the light, render it impossible that they should be identical with it; but he conjectures that there may be a “glow discharge” preceding the main shock, some of the atmospheric particles yielding up their electricity by a gradual process before a discharge of the whole system takes place. In this view, the distinct balls of fire of sensible duration which have been perceived, are produced in a given point or points of a charged system previously to the more general and rapid union of the electrical forces—a supposition which will apply as well to the Mariner’s Lights, or St. Elmo’s Fire, observed during storms of thunder and lightning at sea. Pliny mentions lights noticed by the Roman mariners during tempests, flickering about their vessels, to which Seneca likewise makes allusion. By the superstitions of modern times they have been converted into indications of the guardian presence of St. Elmo, the patron saint of the sailor, hence called cuerpo sante by the Spanish mariners. During the second voyage of Columbus among the West India islands, a sudden gust of heavy wind came on in the night, and his crew considered themselves in great peril, until they beheld several of these lambent flames playing about the tops of the masts, and gliding along the rigging, which they hailed as an assurance of their supernatural protector being near. Fernando Columbus records the circumstance in a manner strongly characteristic of the age in which he lived. “On the same Saturday, in the night, was seen St. Elmo, with seven lighted tapers, at the topmast. There was much rain and great thunder. I mean to say that those lights were seen which mariners affirm to be the body of St. Elmo, on beholding which they chanted many litanies and orisons, holding it for certain, that in the tempest in which he appears, no one is in danger.” A similar mention is made of this nautical superstition in the voyage of Magellan. During several great storms the presence of the saint was welcomed, appearing at the topmast with a lighted candle, and sometimes with two, upon which the people shed tears of joy, received great consolation, and saluted him according to the custom of the Catholic seamen; but he ungraciously vanished, disappearing with a great flash of lightning which nearly blinded the crew.

It is a striking instance of the triumph of mind, that by the introduction of lightning conductors into different civilized states, the power of this most energetic agent of nature is controled, and comparative security provided for life and property, otherwise in imminent jeopardy, when a severe thunder-storm occurs. Experience has taught the prime importance of furnishing exposed or elevated structures with a conducting apparatus, and has sufficiently shown that the immunity from danger enjoyed by many an unprotected building has been merely accidental; for when the teeming thunder-cloud has been wafted within reach of the edifice hitherto unscathed, the delusion has vanished that man may carelessly and with impunity thrust up his handiwork into the region of storms, as if daring the fury of the tempest, and inviting down its vengeance. The fine tower of St. Mark’s, at Venice, rising to the height of 360 feet, terminates in a pyramid which was severely injured in 1388. In 1417 the pyramid was again struck, and set on fire, having been constructed of wood. The same event happened in 1489, when it was entirely consumed. After being rebuilt of stone, the fell lightning renewed its destructive stroke in 1548, 1565, 1653 and 1745; and on the last occasion the whole tower was rent in thirty-seven places, and almost destroyed. It was again ravaged in 1761 and 1762, but in 1766 a lightning rod was put up, which has since protected it from damage. At Glogau, in Silesia, an interesting example of the value of conductors occurred in the year 1782. On the 8th of May, about eight o’clock in the evening, a thunder-storm from the west approached the powder magazine established in the Galgnuburg. An intensely vivid flash of lightning took place, accompanied instantly with such a tremendous peal of thunder, that the sentinel on duty was stupefied, and remained for awhile senseless, but no disaster occurred. Some laborers at a short distance from the magazine saw the lightning issue from the cloud and strike the point of the conductor, which conveyed it in safety by the combustible material. A different result took place with reference to a large quantity of unprotected ammunition, belonging to the republic of Venice, deposited in the vaults of the church of St. Nazaire, at Brescia. The church was struck with lightning in the month of August, 1767, and the electric fluid, descending to the vaults, exploded upward of 207,600 lbs. of powder, reducing nearly one-sixth of the fine city to ruins, and destroying about 3000 of the inhabitants. The Indians, whenever the sky wears a lowering aspect, so as to threaten a severe thunder-storm, are said to leave their pursuits and take refuge under the nearest beech-tree, considering it a complete protection, as it is affirmed that no instance has occurred of the beech having been struck by atmospheric electricity, when other trees of the American forests have been shivered into splinters in its neighborhood.

For ages the inhabitants of the globe have seen the lightning flash and heard the thunder rattle; and some writers upon the occult sciences of the ancients, as Salverte, have supposed that, tutored by experience, without any understanding of the theory of the subject, they possessed the secret of warding off from their buildings the thunderbolt by a conducting apparatus. It is certain that extraordinary intimations to this effect may be culled from their writings. Pliny states that Tullus Hostilius, practicing Numa’s art of bringing down fire from heaven, and performing it incorrectly, was struck with lightning—a fate which Professor Richman of St. Petersburg experienced, while performing incautiously the sublime experiment of Franklin, measuring the strength of the electricity brought down by a metallic rod in a thunder-storm, being instantly killed. Pliny likewise mentions the laurel as the only earthly production which lightning does not strike; hence, as a protection, these trees were planted around the temple of Apollo. Columella, however, mentions white vines surrounding the house of Tarchon, the Etruscan, for the same purpose. These expedients may provoke a smile without deserving one; for there can be no doubt that trees sufficiently high around a temple, or succulent plants covering a dwelling, will exercise to some extent a protective power, and act as a regular system of conductors. Salverte mentions several medals which appear to have reference to this subject, particularly one which represents the temple of Juno, the goddess of the air, the roof of which is armed with pointed rods. He quotes also Michaelis, upon the temple of Jerusalem, to show that the Jews were not unacquainted with the art of protecting their public buildings—a position grounded upon the following facts: “1. That there is nothing to indicate that the lightning ever struck the temple of Jerusalem during the lapse of a thousand years.” This, of course, does not make the fact certain; but when, as M. Arago justly remarks, we consider how carefully the ancient authors recorded the cases in which their public buildings were injured by lightning, we may accept the silence observed respecting the temple of Jerusalem, as proof that it was never struck. For three centuries the cathedral of Geneva, the most elevated in the city, has enjoyed a similar immunity, although inferior buildings have been repeatedly damaged. Saussure discovered the reason of this, in the tower being entirely covered with tinned iron plates, connected with different masses of metal on the roof, and again communicating with the ground by means of metallic pipes. “2. That according to the account of Josephus, a forest of spikes with golden or gilt points, and very sharp, covered the roof of this temple; a remarkable feature of resemblance with the temple of Juno represented on the Roman medals. 3. That this roof communicated with the caverns in the hill of the temple, by means of metallic tubes, placed in connection with the thick gilding that covered the whole exterior of the building; the points of the spikes there necessarily producing the effect of lightning-rods. How are we to suppose that it was only by chance they discharged so important a function; that the advantage received from it had not been calculated; that the spikes were erected in such great numbers only to prevent the birds from lodging upon and defiling the roof of the temple? Yet this is the sole utility which the historian Josephus attributes to them.” Upon a sober review of these facts, it is difficult to resist the conclusion that the ancient world had some proficiency in the art of guiding the electric fluid from the bosom of the clouds, conducting it in a prescribed course, and thus disarming it of its terrors.

The subject of electrical agency is intimately connected with that of magnetism, to which this is the fittest place to glance—one of the most recondite points of physical science. The relation between the two is evident, from the notorious fact that lightning often renders steel magnetic, and disturbs the magnetism of the magnetised needle, so that in thunder-storms the compass needles of a ship have frequently been seriously injured. The magnetic agency, like electricity, has a general distribution over the earth, but the phenomena differ in different parts of the world, and are subject to periodical differences in the same place, the cause of which is very little understood. Every one is acquainted with the polarity of a freely suspended magnetic needle, or its tendency to lie parallel with the earth’s axis, pointing nearly north and south in every region of the globe. What is called the dip or inclination of the needle is its divergence from a perfectly horizontal position. Thus the north pole of the needle inclines downward in the latitude of London at an angle of 70°, but conveyed toward the equator, the dip diminishes, till no inclination at all appears. Transported farther toward the south, the dip again discovers itself, but in an opposite direction, the south pole of the needle inclining downward. “To understand the reason of this dip of the magnetic needle, and of its general direction, we have only to consider that the earth itself operates as a great magnet, the poles of which are situated beneath its surface. The directive property of the needle is owing to these poles; and when the needle is on the north side of the equator, the north pole of the earth having the greatest effect, the needle is attracted downward toward the north pole; hence exactly over the magnetic pole the needle would be vertical. Similar phenomena occur in the southern hemisphere; but here the south pole predominates, and of course depresses the corresponding pole of the needle; while at the magnetic equator, from the equal action of both poles, the needle will assume an exactly horizontal position.”

But neither the magnetic equator nor the magnetic poles coincide precisely with the geographical equator and poles, and this difference constitutes what is termed the variation of the needle. From calculation, the north magnetic pole had been fixed in latitude 70°, and longitude 98° 30′ west, a spot which Commander Ross approached within the distance of ten miles, in the year 1830, but was unable to verify the site, for want of the requisite instruments. Upon going through a long series of calculations afterward himself, he concluded the above position to have been erroneously assigned, and that the real point lay in latitude 70° 5′ 17″ north, and longitude 96° 46′ 45″ west, a spot on the western coast of Boothia, which he prepared to reach. On the first of June, 1831, at eight o’clock in the morning, he arrived at the site to which his calculations pointed, and found the same day the amount of the dip to be 89° 59′, only one minute less than 90°, the vertical position, which would have precisely indicated the polar station; and the horizontal needles, suspended in the most delicate manner possible, did not betray the slightest movement. The spot was an unattractive level site along the coast, rising into ridges from fifty to sixty feet high, about a mile inland. The wish expressed by the discoverer was natural, that a place so important had possessed more of mark or note, but Nature had erected no monument to denote the spot which she had chosen as the centre of one of her “great and dark powers.” A cairn of some magnitude was constructed by the adventurers, upon which the British flag was planted, and underneath, a canister was buried, containing a record of the interesting enterprise.

Aurora Borealis—Loch Leven.

Aurora Borealis.

Halos.