Part 79

"Towards the north-west, whence the eclipse came, I could not in the least find any distinction in the horizon between heaven and earth, for a good breadth of about sixty degrees, or more; nor the town of Amsbury underneath us, nor scarcely the ground we trod on. I turned myself round several times during this total darkness, and remarked at a good distance from the west on both sides, that is, to the north and south, the horizon very perfectly; the earth being black, the lower parts of the heavens light; for the darkness above hung over us like a canopy, almost reaching the horizon in those parts, or as if made with skirts of a lighter colour; so that the upper edges of all the hills were as a black line, and I knew them very distinctly by their shape or profile; and northward, I saw perfectly, that the interval of light and darkness in the horizon was between Martinsal-hill and St. Ann's-hill; but southward it was more indefinite. I do not mean that the verge of the shadow passed between those hills, which were but twelve miles distant from us; but, so far I could distinguish the horizon; beyond it not at all. The reason of it was this; the elevation of ground I was upon gave me an opportunity of seeing the light of the heavens beyond the shadow; nevertheless, this verge of light looked of a dead yellowish, and greenish colour; it was broader to the north than south; but the southern was of a tawny colour: at this time behind us, or eastward toward London, it was dark too, where otherwise I could see the hills beyond Andover; for the foremost end of the shadow was past thither; so that the whole horizon was now divided into four parts of unequal bulk, and degrees of light and dark; the part to the north-west broadest and blackest, to the south-west lightest and longest. All the change I could perceive during the totality, was, that the horizon by degrees drew into two parts, light and dark: the northern hemisphere growing still longer, lighter, and broader; and the two opposite dark parts uniting into one, and swallowing up the southern enlightened part.

"As at the beginning the shade came feelingly upon our right shoulders, so now the light from the north, where it opened as it were; though I could discern no defined light or shade upon the earth that way, which I earnestly watched for, yet it was manifestly by degrees, and with oscillation, going back a little, and quickly advancing further, till at length, upon the first lucid point appearing in the heavens, where the sun was, I could distinguish pretty plainly a rim of light running alongside of us a good while together, or sweeping by at our elbows from west to east. Just then, having reason to suppose the totality ended with us, I looked on my watch, and found it to be full three minutes and a half more. Now the hill-tops changed their black into blue again, and I could distinguish an horizon where the centre of darkness was before: the men cried out, they saw the copped-hill again, which they had eagerly looked for; but still it continued dark to the south-east, yet I cannot say that ever the horizon that way was undistinguishable. Immediately we heard the larks chirping, and singing very briskly, for joy of the restored luminary, after all things had been hushed into a most profound and universal silence. The heavens and earth now appeared exactly like morning before sunrise, of a greyish cast, but rather more blue interspersed; and the earth, so far as the verge of the hill reached, was of a dark green, or russet colour.

"As soon as the sun emerged, the clouds grew thicker, and the light was very little amended for a minute or more, like a cloudy morning slowly advancing. After about the middle of the totality, and so after the emersion of the sun, we saw Venus very plainly, but no other star. Salisbury steeple now appeared; but the clouds never removing, we could take no account of it afterwards; but in the evening it lightened very much. I hastened home to write this letter, and the impression was so vivid upon my mind, that I am sure, I could for some days after have written the same account of it, and very precisely. After supper I made a drawing of it from my imagination, upon the same paper on which I had taken a prospect of the country before.

"I must confess to you, that I was (I believe) the only person in England, that regretted not the cloudiness of the day, which added so much to the solemnity of the sight, and which incomparably exceeded, in my apprehension, that of 1715, which I saw very perfectly from the top of Boston steeple, in Lincolnshire, where the air was very clear; but the night of this was more complete and dreadful: there, indeed, I saw both sides of the shadow come from a great distance, and pass beyond us to a considerable extent; but this eclipse had much more of variety and majestic terror; so that I cannot but felicitate myself upon the opportunity of seeing these two rare accidents of nature, in so different a manner. Yet I should willingly have lost this pleasure, for your more valuable advantage of perfecting the noble theory of the celestial bodies, which, last time, you gave the world so nice a calculation of; and I wish the sky had now as much favoured us for an addition to your honour and great skill, which I doubt not to be as exact in this as before."

We now proceed to describe THE HALO, OR CORONA; AND SIMILAR APPEARANCES.--An Halo is a luminous circle surrounding the sun, moon, planets, or fixed stars. Occasionally these circles are white, and sometimes they are coloured like the rainbow. Sometimes one only is visible, and at others several concentric halos appear at the same time. Mr. Huygens observed red next the sun, and a pale blue outwards. Sometimes they are red on the inside, and white on the outside. In France, one was observed in 1683, the middle of which was white; after which followed a border of red, next to it was blue, then green, and the outermost circle was a bright red. In 1728, one was seen of a pale red outwardly, then followed yellow, and then green, terminated by a white. In Holland, M. Muschenbroek says, fifty may be seen in the day-time, almost every year; but they are difficult to be observed, except the eye be so situated, that not the body of the sun, but only the neighbouring parts of the heavens, can be seen. Mr. Middleton says, that this phenomenon is very frequent in North America; for that there is generally one or two about the sun every week, and as many about the moon every month. Halos round the sun are very frequent in Russia. M. Æpinus says, that from the 23d of April, 1758, to the 20th of September, he himself had observed no less than twenty-six, and that he has sometimes seen twice as many in the same space of time.

Similar, in some respects, to the halo, was the remarkable appearance which M. Bouguer describes, as observed on the top of Mount Pichinca, in the Cordilleras. When the sun was just rising behind them, so as to appear white, each of them saw his own shadow projected upon it, and no other. The distance was such, that all the parts of the shadow were easily distinguishable, as the arms, the legs, and the head; but what surprised them most was, that the head was adorned with a kind of glory, consisting of three or four small concentric crowns, of a very lively colour, each exhibiting all the varieties of the primary rainbow, and having the circle of red on the outside. The intervals between these circles continued equal, though the diameters of them all were constantly changing. The last of them was very faint; and at a considerable distance was another great white circle, which surrounded the whole. This phenomenon never appeared but in a cloud consisting of frozen particles, and never in drops of rain like the rainbow. When the sun was not in the horizon, only part of the white circle was visible, as M. Bouquer frequently observed afterwards. Similar to this curious appearance, was one seen by Dr. M'Fait in Scotland; who observed a rainbow round his shadow in the mist, when he was upon an eminence above it. In this situation the whole country round seemed buried under a vast deluge, and nothing but the tops of distant hills appeared here and there above the flood. In those upper regions, the air, he says, is at that time very pure and agreeable. At another time he observed a double range of colours round his shadow. The colours of the outermost range were broad and very distinct, and every where about two feet distant from the shadow. Then there was a darkish interval, and after that another narrower range of colours, closely surrounding the shadow, which was very much contracted. He thinks that these ranges of colours are caused by the inflection of the rays of light, the same that occasions the ring of light which surrounds the shadow of all bodies, observed by M. Maraldi, and others.

We next proceed to the phenomenon generally called FALLING OR SHOOTING STAR.--This is a luminous meteor, darting rapidly through the air, and resembling a star falling from the heavens. The explication of this phenomenon had puzzled all philosophers, till the modern discoveries in electricity led to the most probable account of it. Signior Beccari makes it pretty evident, that it is an electrical appearance, and recites the following fact in proof of his opinion. About an hour after sunset, he, and some friends that were with him, observed a falling star directing its course towards them, and apparently growing larger and larger, but it disappeared not far from them. When it vanished, it left their faces, hands, and clothes, with the earth, and all the neighbouring objects, suddenly illuminated with a diffused and lambent light, but not attended with any noise. During their surprise at this appearance, a servant informed them, that he had seen a light shine suddenly in the garden, and especially upon the streams which he was throwing to water it. All these appearances were evidently electrical; and Beccari was confirmed in his conjecture, that electricity was the cause of them, by the quantity of electric matter which he had seen gradually advancing towards a kite he had elevated, which had very much the appearance of a falling star. Sometimes, also, he saw a kind of glory round the kite, which followed it when it changed its place, but left some light, for a small space of time, in the place it had quitted.

Captain Bagnold says, whilst passing through the straits of Bahama, in the autumn of 1799, he witnessed the following singular atmospheric phenomenon.

"It was a fine star-light morning, about two o'clock, the atmosphere remarkably clear, with a light air from the north-east; the sky to windward, from north-north-east to south-south-east, was illuminated by a profusion of those meteors, vulgarly denominated falling stars, but of a description far more vivid than those usually seen in the higher latitudes; the head of each was an oblong ignited mass, followed by a long luminous tail, which, after three or four seconds, gradually vanished. They were formed, to all appearance, in the air, at an elevation of from thirty-five to sixty-four degrees, none being observed in the zenith, and few to commence nearer the horizon than the first-mentioned angles. At the mean of these elevations, the greatest numbers were seen darting in different directions, forming portions of a large curve, all slightly inclined to the horizon. Multitudes were constantly visible at the same moment, and they succeeded each other so rapidly, that the eye of the spectator was kept in motion between the above points of the compass. In about ten minutes they became less frequent, and at length ceased altogether.

"The apparent distance of this phenomenon would, by a seaman, be estimated at fifteen or twenty miles; and if it really was what I have always considered it, namely, a nocturnal shower of meteoric stones, it was perhaps fortunate for all on board, that we were not within the sphere of its action: whatever it was, never shall I forget the splendour of the spectacle."--See _Humboldt's Personal Narrative_, volume III. page 331, 335.

We close this chapter with AN ACCOUNT OF THREE VOLCANOES IN THE MOON; by Dr. Herschel.

"It will be necessary to say a few words by way of introduction to the account I have to give of some appearances upon the moon. The phenomena of nature, especially those that fall under the inspection of the astronomer, are to be viewed, not only with the usual attention to facts as they occur, but with the eye of reason and experience. In this we are, however, not allowed to depart from plain appearances, though their origin and signification should be indicated by the most characterizing features. Thus, when we see on the surface of the moon a great number of elevations, from half a mile to a mile and a half in height, we are strictly entitled to call them mountains; but when we attend to their particular shape, in which many of them resemble the craters of our volcanoes, and thence argue that they owe their origin to the same cause which has modelled many of these, we may be said to see by analogy, or with the eye of reason. Now, in this latter case, though it may be convenient, in speaking of phenomena, to use expressions that can only be justified by reasoning upon the facts themselves, it will certainly be the safest way not to neglect a full description of them, that it may appear to others how far we have been authorized to use the mental eye. This being premised, I may safely proceed to give my observations.

"April 19th, 1787, 10h. 36', sidereal time: I perceive three volcanoes in different places of the dark part of the new moon. Two of them are either already nearly extinct, or otherwise in a state of going to break out; which, perhaps, may be decided next lunation. The third shews an actual eruption of fire, or luminous matter. I measured the distance of the crater from the northern limb of the moon, and found it 3' 57".3. Its light is much brighter than the nucleus of the comet which M. Mechain discovered at Paris the 10th of this month.--April 20th, 1787, 10h. 2', sidereal time: The volcano burns with greater violence than last night. I believe its diameter cannot be less than 3", by comparing it with that of the Georgian planet: as Jupiter was near at hand, I turned the telescope to his third satellite, and estimated the diameter of the burning part of the volcano to be equal to at least twice that of the satellite. Hence we may compute that the shining or burning matter must be above three miles in diameter. It is of an irregular round figure, and very sharply defined on the edges. The other two volcanoes are much farther towards the centre of the moon, and resemble large pretty faint nebulæ, that are gradually much brighter in the middle; but no well-defined luminous spot can be discerned in them. These three spots are plainly to be distinguished from the rest of the marks upon the moon; for the reflection of the sun's rays from the earth is, in its present situation, sufficiently bright, with a ten-feet reflector, to shew the moon's spots, even the darkest of them; nor did I perceive any similar phenomena last lunation, though I then viewed the same places with the same instrument.

"The appearance of what I have called the actual fire, or eruption of a volcano, exactly resembled a small piece of burning charcoal, when it is covered by a very thin coat of white ashes, which frequently adhere to it after it has been some time ignited; and it had a degree of brightness about as strong as that with which such a coal would be seen to glow in faint daylight. All the adjacent parts of the volcanic mountain seemed to be faintly illuminated by the eruption, and were gradually more obscure as they lay at a greater distance from the crater.

"This eruption resembled much that which I saw on the fourth of May, in the year 1783; an account of which, with many remarkable particulars relating to volcanic mountains in the moon, I shall take an early opportunity of communicating to the Royal Society. It differed, however, considerably in magnitude and brightness; for the volcano of the year 1783, though much brighter than that which is now burning, was not near so large in the dimensions of its eruption; the former seen in the telescope resembled a star of the fourth magnitude, as it appears to the natural eye: this, on the contrary, shews a visible disk of luminous matter, very different from the sparkling brightness of star-light."

CHAP. LXIX.

CURIOSITIES RESPECTING VARIOUS PHENOMENA, OR APPEARANCES IN NATURE.--(_Concluded._)

_The Aurora Borealis._

Silent from the north A blaze of meteors shoots: ensweeping first The lower skies, they all at once converge High to the crown of heav'n, and all at once Relapsing quick, as quickly reascend, And mix and thwart, extinguish and renew, All ether coursing in a maze of light _Thomson._

THE AURORA BOREALIS, sometimes called Streamers, is an extraordinary meteor, or luminous appearance, shewing itself in the night time in the northern part of the heavens; and most usually in frosty weather. It is generally of a reddish colour, inclining to yellow, and sends out frequent corruscations of pale light, which seem to rise from the horizon in a pyramidical undulating form, and shoot with great velocity up to the zenith. The Aurora Borealis appears frequently in form of an arch, chiefly in the spring and autumn, after a dry year. The arch is partly bright, partly dark, but generally transparent: and the matter of which it consists, is also found to have no effect on rays of light which pass through it. Dr. Hamilton observes, that he could plainly discern the smallest speck in the Pleiades through the density of those clouds which formed the Aurora Borealis in 1763, without the least diminution of its splendour, or increase of twinkling.

This kind of meteor, which is more uncommon as we approach towards the equator, is almost constant during the long winter, and appears with the greatest lustre in the polar regions. In the Shetland isles, the "Merry Dancers," as the northern lights are there called, are the constant attendants of clear evenings, and afford great relief amidst the gloom of the long winter nights. They commonly appear at twilight, near the horizon, of a dun colour, approaching to yellow; they sometimes continue in that state for several hours, without any perceptible motion; and sometimes they break out into streams of stronger light, spreading into columns, and altering slowly into ten thousand different shapes, and varying their colours from all the tints of yellow, to the most obscure russet. They often cover the whole hemisphere, and then exhibit the most brilliant appearance. Their motions at this time are most amazingly quick; and they astonish the spectator with the rapid changes of their form. They break out in places where none were seen before, skimming briskly among the heavens, are suddenly extinguished, and are succeeded by a uniform dusky tract. This again is brilliantly illuminated in the same manner, and as suddenly left a dark space. In some nights, they assume the appearance of large columns, on one side of the deepest yellow, and on the other, gradually changing, till it becomes undistinguished from the sky. They have generally a strong tremulous motion from one end to the other, and this continues till the whole vanishes.

As for us, who see only the extremities of these northern phenomena, we can have but a faint idea of their splendour and motions. According to the state of the atmosphere, they differ in hue; and sometimes assuming the colour of blood, they make a dreadful appearance. The rustic sages who observe them, become prophetic, and terrify the spectators with alarms of war, pestilence, and famine. Nor, indeed, were these superstitious presages peculiar to the northern islands: appearances of a similar nature are of ancient date; and they were distinguished by the appellations of "phasmata," "trabes," and "balides," according to their forms and colours. In old times they were either more rare, or less frequently noticed: they were supposed to portend great events, and the timid imagination formed of them aërial conflicts.

In the northern latitudes of Sweden and Lapland, the Auroræ Boreales are not only singularly beautiful in their appearance, but they afford travellers, by their almost constant effulgence, a very beautiful light during the whole night. In Hudson's Bay the Aurora Borealis diffuses a variegated splendour, which is said to equal that of the full moon. In the northeastern parts of Siberia, according to the description of Gmelin, these northern lights are observed to "begin with single bright pillars, rising in the north, and almost at the same time in the north-east, which, gradually increasing, comprehend a large space of the heavens, rush about from place to place with incredible velocity, and, finally, almost cover the whole sky up to the zenith, and produce an appearance as if a vast tent were expanded in the heavens, glittering with gold, rubies, and sapphire. A more beautiful spectacle cannot be painted; but whoever should see such a northern light for the first time, could not behold it without terror. For, however fine the illumination may be, it is attended, as I have learned from the relation of many persons, with such a hissing, crackling, and rushing noise through the air, as if the largest fire-works were played off. To describe what they then hear, they make use of the expression, 'The raging host is passing.' The hunters, who pursue the white and blue foxes in the confines of the Icy Sea, are often alarmed in their course by these northern lights. Their dogs are then so much frightened, that they will not move, but lie obstinately on the ground, till the noise has passed. Commonly, clear and calm weather follows this kind of northern lights. This account has been confirmed by the uniform testimony of many, who have spent part of several years in these northern regions, and inhabited different countries from the Yenisei to the Lena; so that no doubt of its truth can remain. This seems, indeed, to be the real birth-place of the Aurora Borealis."

A person who resided seven years at Hudson's Bay, confirms M. Gmelin's relation of the fine appearance and brilliant colours of the northern lights, and particularly of their rushing noise, which he affirms he has frequently heard, and he compares it to the sound produced by whirling round a stick swiftly at the end of a string. A similar noise has likewise been noticed in Sweden. Mr. Nairne also, being in Northampton at the time when the northern lights were remarkably bright, is confident he heard a hissing or whizzing sound. Mr. Belknap, of Dover, in New Hampshire, North America, testifies to this fact. M. Cavallo says, that the cracking noise is distinctly audible, and that he has heard it more than once. Similar lights, called Auroræ Australes, have been long since observed towards the south pole, and their existence has been lately ascertained by Mr. Forster, who assures us, that in his voyage round the world with Captain Cook, he observed them in high southern latitudes, though attended with phenomena somewhat different from those which are seen here.