Volume 7 / Part 2 — Philosophical Transactions of the Royal Society of London, for the year 1827. Part II. ◊

Philosophical Transactions of the Royal Society of London, for the year 1827. Part II. ◊

The following are the contents of this Part of the Society’s Transactions:—

On a new form of the differential thermometer, with some of its applications. By William Ritchie, A.M., rector of Tain Academy. Communicated by J. F. W. Herschel, Esq., Sec. R.S.

On the structure and use of the submaxillary odoriferous gland in the genus Crocodilus. By Thomas Bell, Esq., F.L. and G.S.S. Communicated by Sir Everard Home, Bart, V.P.R.S.

On the permeability of transparent screens of extreme tenuity of radiant heat. By William Ritchie, A.M., rector of Tain Academy. Communicated by J. F. W. Herschel, Esq., Sec. R.S. [p380]

On the derangement of certain transit instruments by the effects of temperature. By Robert Woodhouse, A.M., F.R.S., &c.

On some of the compounds of chromium. By Thomas Thomson, M.D., F.R.S. L. and E., Professor of Chemistry, Glasgow.

Rules and principles for determining the dispersive ratio of glass; and for computing the radii of curvature for achromatic object-glasses, submitted to the test of experiment. By Peter Barlow, Esq., F.R.S., Mem. Imp. Ac. Petrop, &c.

On the change in the plumage of some hen-pheasants. By William Yarrell, Esq., F.L.S. Communicated by William Morgan, Esq., F.R.S.

On the secondary deflections produced in a magnetised needle by an iron-shell, in consequence of an unequal distribution of magnetism in its two branches. First noticed by Captain J. P. Wilson, of the Honourable East India Company’s ship Hythe. By Peter Barlow, Esq., F.R.S., Mem. Imp. Sc. Petrop.

On the difference of meridians of the royal observatories of Greenwich and Paris. By Thomas Henderson, Esq. Communicated by J. F. W. Herschel, Esq., Sec. R.S.

Some observations on the effects of dividing the nerves of the lungs, and subjecting the latter to the influence of voltaic electricity. By A. P. W. Philip, M.D., F.R.S. L. and E.

On the effects produced upon the air-cells of the lungs when the pulmonary circulation is too much increased. By Sir Everard Home, Bart., V.P.R.S.

Theory of the diurnal variation of the magnetic-needle, illustrated by experiments. By S. H. Christie, Esq., M.A., F.R.S.

On the ultimate composition of simple alimentary substances; with some preliminary remarks on the analysis of organized bodies in general. By William Prout, M.D., F.R.S.

A Practical Treatise on the use of the Blowpipe in chemical and mineral analysis; including a systematic arrangement of simple minerals, adapted to aid the student in his progress in mineralogy, by facilitating the discovery of the names of species. By John Griffin, Author of Chemical Recreations. Glasgow, 1827. ◊

PERFORMING with the blowpipe is something like playing upon the fiddle—it looks mighty easy, but for its perfect accomplishment requires a combination of skill and dexterity which practice alone can confer. We are disposed, therefore, to think lightly of those essays upon the subject which pretend to instruct the beginner in the actual use of the instrument; telling him how he is to puff out his cheeks, breathe through his nose, make a valve of his tongue, and keep up a [p381] perpetual stream through the nozzle of the tube; all which is much easier described than done, and is entirely matter of experimental acquisition, more easily attained without than with the usual instructions. In the little work before us, all these matters are passed over with fit brevity, and the attention of the student is chiefly directed to the appearances which different substances exhibit before the blowpipe, and by which minerals may be distinguished and classed. The history of these constitute the bulk of Mr. Griffin’s duodecimo, being preceded only by a few remarks upon the different kinds of blowpipe, respecting which we have merely to observe that justice is not done to Mr. Newman, who first suggested what is here called “Dr. Clarke’s blowpipe;” indeed elsewhere the author seems a little angry with Mr. Children for recommending Mr. Newman’s apparatus. We observe, moreover, that no notice is taken of Mr. Newman’s and several other papers on the blowpipe, which have appeared in the old series of this Journal; nor of Dr. Clarke’s original Essay, published in the second volume of that work, from which, and sundry other symptoms, we conclude that Mr. Griffin is a pupil of Dr. Thomas Thomson. Be this as it may, we bear him no malice, and very conscientiously recommend his book to the mineralogical student, as a valuable and clear epitome of what relates to the behaviour of substances before the blowpipe.

Circle of the Seasons, and Perpetual Key to the Calendar and Almanack; to which is added the Circle of the Hours and History of the Days of the Week, being a compendious Illustration of the History, Antiquities, and Natural Phenomena of each Day in the Year. London, 1828. Small 8vo. ◊

THE title of this book may lead our readers to suspect it as an interloper among works on science; but it touches upon many points of scientific inquiry, and upon botany especially, and is compiled with so much evident labour and accuracy, as to merit recommendation. The saints and festivals of each day are recorded, by which we make the acquaintance of many worthy persons and curious anecdotes; there is also a brief natural history of each day, containing short notices of the plants which on an average begin to flower or to fade, and of the birds which arrive or begin to sing. [p382] The merits of the descriptive poetry, which is thickly interspersed, we leave to other critics. Those who are destined to live in the “fuliginous tenebrosity” of this smoke-saturated metropolis, and to breathe an atmosphere “sated with exhalations rank and fell,” care little about the first peeping forth of the modest snowdrop, or the early bursting of the golden crocus; but such as reside in the country will be glad to have their attention pleasingly directed to the successive products of the field, the flower-garden, and the green-house.

Conversations on the Animal Economy. By a Physician. 2 vols. small 8vo. London, 1827. ◊

WE have more than once expressed our opinion on the subject of conveying information to young people in the way of “Conversations,” which in the present volumes are carried on between Dr. A., Harriet, Sophia, and Charles; they are at once instructive and amusing, and evidently the produce of one possessed of much information upon the subjects discussed, and, what is more to the point, of the art of pleasantly and intelligibly conveying it.

The Conversations open with an account of the coverings or integuments of animals; their arrangements by systematic writers are then adverted to, and a short but useful description is given of the varieties of mankind, as enumerated by Blumenbach and illustrated by Camper. The bones and muscles form the subjects of the fifth and sixth conversations; they are concisely described, and with sufficient accuracy. The brain and nervous system and the organs of sense are next talked about. The doctrines of phrenology are fairly explained; and in the conversations on smell and taste, vision, hearing, and touch, the anatomy of the respective organs, and their varieties in the different animal tribes are treated of, the dulness of the details being relieved by physiological illustrations. The remaining conversations are occupied with an account of the principal functions of animals, and of the several organs chiefly concerned in their performance; the varieties of teeth and stomachs are here treated of, and the structures of the heart and blood-vessels, as concerned in circulation and respiration. The production of heat by animal systems is then noticed; and the twentieth and concluding conversation is employed in the exposition of the general phenomena of growth and decay. [p383]

We have thus briefly stated the contents of these volumes, which are further illustrated by numerous woodcuts and several plates; and are perfectly ready to commend the performance as an extremely useful and proper book for young persons, but not, in our opinion, of both sexes: we should have been better pleased if Harriet and Sophy had been replaced by William and Thomas; for we cannot fancy the subjects here discussed as quite fit for young ladies. Boys, on the contrary, ought to know much more of these matters than they commonly do; and for conveying such information in a pleasing and familiar, yet neither vulgar nor superficial style, this compilation seems perfectly appropriate, and will, we trust, find, as it ought, a numerous class of readers.

Notice of a New Genus of Plants discovered in the Rocky Mountains of North America by Mr. David Douglas. By John Lindley, Esq., F.L.S., &c. &c. ◊

Upon his journey across the rocky mountains in April 1827, in latitude 52° N., longitude 118° W., at an estimated elevation of 12,000 feet above the level of the sea, the attention of Mr. Douglas was attracted by a brilliant purple patch amidst the surrounding snow. On approaching it, he was surprised to find that the colour which had arrested his eye was caused by the blossoms of a little plant, from which the superincumbent snow had not yet melted away. The well-known Saxifraga oppositifolia immediately occurred to his recollection, and he at first imagined he had either discovered that species, or one nearly allied to it; but upon a closer inspection, he perceived that it was no Saxifraga, but a genus apparently new. Specimens having been submitted to me for examination since Mr. Douglas’s return, the following description has been drawn up:—

The plant forms a thick tuft consisting of numerous perennial branched stems, the lower of which are covered with the persistent decayed leaves and fruit of previous summers. The stems are round, bright purplish brown, covered with scattered, rigid, branched, short hairs, and densely clothed with opposite spreading leaves. The leaves are a dull glaucous green, semi-amplexicaul, [p384] linear, obtuse, about five lines long and three-quarters of a line broad, so closely covered with hairs like those of the stem, that the whole epidermis is hidden. Their veins are concealed by the hairs; but if the latter are removed, they appear to consist of a thickened mid-rib, and a few nearly simple spreading venæ primariæ. The flowers proceed from the axillæ of the upper leaves, from three to six on each little branch; at first they are sessile, but their foot-stalks subsequently lengthen by degrees until the fruit is ripe, when they are from three-quarters of an inch to one inch in length, and covered with the same sort of hairs as the leaves and stem. The calyx is hairy in like manner, obconical, angular, with five equal erect narrowly triangular teeth, about the length of the tube. The corolla is of a vivid purple colour, infundibuliform, wholly destitute of pubescence; the tube is a little ventricose and rather longer than the calyx, its whole length being about three lines; the limb is spreading, five-parted with cuneate, oblong, obtuse, segments; the orifice is guarded by five transversely linear calli, placed under each sinus, and corresponding to the same number of external depressions of the neck of the tube. The anthers are linear oblong, nearly sessile, opposite the segments of the corolla, and a little enclosed within the tube. The ovarium is superior, of an obovate figure, one-celled, with a central, free, fungilliform placenta, the lower edge of which has five teeth corresponding to an equal number of peltate ovula; the style is filiform, as long as the tube of the corolla, and continuous with the ovarium; stigma, a minute depressed cup. The capsule is of a cartilaginous texture, surrounded by the persistent calyx; one-celled, with five recurving valves; the seeds are two, peltate, oblong, convex on the outside, concave in the inside, dark brown, covered closely with minute dots or depressions; four only having been found, their internal organization has not been determined.

Hence it appears that, with the exception of the interior of the seed, the whole structure of the plant is determinable: it is also obvious that it is referable to Primulaceæ, of which it possesses all the characters. In fact it is closely akin both to Primula and Androsace. From both these genera, however, [p385] its ovarium which exhibits the greatest instance of reduction of ovula yet known in the order, and its dispermous capsule, with oblong concave seeds, readily and essentially distinguish it.

I have, therefore, named it after its indefatigable discoverer, whose active and successful researches in its native country, richly entitle him to the distinction.

DOUGLASIA.

NAT. ORD. Primulaceæ; inter Primulam et Androsacen.

Calyx obconicus, angulatus, 5-dentatus. Corolla infundibularis, tubo ventricoso, limbo plano 5-partito, fauce callo lineari sub utroque sinu. Ovarium uniloculare placentâ centrali liberâ pedicellatâ fungilliformi, margine 5-dentato; ovula 5 dentibus placentæ opposita. Capsula vestita, unilocularis, 5-valvis. Semina duo concava scrobiculata.—Cæspes suffruticulosus (Americæ borealis), foliis indivisis, pube rigidâramosâ, floribus axillaribus solitariis.

Sp. 1. Douglasia nivalis.

A Description of the Aurora Borealis seen in London on the Evening and Night of the 25th of September, 1827; with Critical Remarks upon other Descriptions of the same, and previous Appearances of the Meteor, both in the Northern and Southern Hemispheres. By E. A. Kendall, Esq., F.S.A. ◊

ON the evening and right of the 25th of September last, the horizon of the metropolis, toward the north, and toward the north-west and the north-east, exhibited a remarkable display of the meteor or phenomenon called, after the example of the Italian philosopher Gassendi, Aurora Borealis.

The weather, for many days preceding, had been mild, with alternate sunshine, clouds, and showers. The wind had been generally in the west and south-west quarters; though on the 18th and 19th it was in the north-west, and on the 20th in the north-east. The barometer, at three o’clock in the afternoon, had stood at from 30° 40′ to 30° 20′, to which latter height it had descended on the 20th; and, from that day to the 25th, it had remained, at 29° 90′ and 29° 75′. The thermometer, at the same hour, between the 14th and the 20th, had ranged between 65° 6′ and 59° 2′; and it stood, on the 25th, at 59° 6′, with the wind in the south-west. The sky, toward the zenith, on the evening of that day, was [p386] partially clear, and partially covered with shifting clouds. On the north, and on the west and east of north, heavy and stationary clouds blackened the whole horizon, to an elevation of more than five degrees; and the southern hemisphere was dark with dark clouds from the horizon to the zenith.

I. By some, the Aurora was seen from the time when the sun was set; but the first appearance in the heavens, which attracted the attention of the present writer, whose situation at the moment shut out from him the horizon upon all sides but the west, was that of a certain breadth of red or copper-coloured light, or of light of a colour nearly resembling that reflected by an ordinary conflagration of buildings, pointing upward from the west. The colour, indeed, was dissimilar from that which is usual upon the occurrence of a fire on a cloudy night; yet, in the absence of any other immediate explanation, he should not have hesitated so to understand it, except for the figure within which it was circumscribed, and which, instead of being diffusive, and less and less conspicuous toward its extremities, or rounded in its outline, like masses of ruddy smoke, had the peculiarities of an equal breadth, rectilinear sides, a square top, and sharp outlines. Its height was continually increasing; but not even that phenomenon, nor even the curve to the eastward, across the heavens, and which it presently began to add to its figure, were appearances absolutely to dissipate the illusion of the existence of a fire; and it was scarcely, therefore, till this breadth of colour, throwing itself entirely over the heavens, and descending, at its projected extremity, toward the east, formed an arch, of which, perhaps, the elevation was seventy degrees, (which was not the work of many minutes, the motion, at the same time, being visible, but of moderate rapidity,) that its real character of a natural phenomenon distinctly impressed itself upon the mind of the present writer, its observer. While this, however, was proceeding, the road which he was pursuing had brought him more into view of the north-western and northern horizon; and, then, the light in the north, and to the west of north, which, from behind the clouds that lined the horizon, seemed like the light of a rising moon, or of the [p387] breaking day, together with the vertical projection of rays of light, beneath and above the arch, removed every doubt as to the cause of the appearance, by demonstrating its connexion with an Aurora Borealis.

It was now about a quarter past eleven o’clock. The sky, beneath the lower or inner edge of the arch, was clear and star-light, and, through the contrast created by the ruddy colour placed against it, appeared of a lively blue. The upper edge of the arch, in the meantime, was relieved only by the dark gray of the clouds, which, with more or less continuity, overhung the upper part of the heavens. But these latter were now dispersing; the cloudless zenith, which presently afterwards disclosed itself, was now progressively and swiftly preparing; and, as the clouds moved and fled, the outlines of the arch lost their sharpness, the colour changed, from that of fire or of copper, to something more or less of purple or of the rose; it spread itself in the vapour, and with the vapour vanished.

II. But this was only the curtain of the stage, behind the folds of which the true scene had its existence. This latter, still concealed, to a certain and uniform height, by a parapet, as it were, of dark and unbroken clouds, consisted, first, in the ground of white light, already described as resembling that of a sky in the midst of which clouds shut out the disk of the moon, or rather that in which the rising sun is just about to appear; and, secondly, in a range of columns, or fountains, or jets of light, more coloured than the ground, which, rising from behind the ridge or parapet of clouds, and from and in the midst of the white light, formed, together, not the figure which would have been produced by their uniform convergence toward the zenith, but one which bore some resemblance to that assumed by the sticks of a fan, or still more to the appearance of stalks in a flower-basket, or in a sheaf of corn. For, in this manner, the column, which, in general terms, may be called the central one, and which arose in the due north, was vertical, and therefore projected toward the zenith; while those which extended from it upon either side, that is, toward the west or toward the east, gradually inclined more and more [p388] toward the horizon on their respective sides; and, as to the outer columns on the east, inclined, not in rectilinear figures, but in curves more or less decided. In these columns or coruscations several particulars were to be remarked.

1. That, within the space of from one hour to two, the whole group appeared to traverse the horizon together, from the west of north to the east of north, as if upon one movable base, or as if the source of their appearance became gradually exhausted to the west of north, and grew gradually into activity upon the east of north; alternatives of explanation, however, which might materially affect the theory of their production. During the whole change, in the meantime, the north preserved its splendour, appearing uniformly as the focus of the fire, or as the pivot of the machine, or as the well from which all else was supplied. The change consisted in the appearance of columns, of more or less magnitude, strength, and brightness, more or less advanced from the north toward the west, or from the north toward the east; but the north, during all this variation, suffered no other change than this, that whereas, in the beginning of the evening, the greater portion of columns rose to its west, while, in the latter part of the night, the greater portion arose to its east. But, besides this general configuration, and this united motion of the meteor, there was to be observed, in the several columns themselves, both the variations of colour which distinguished one from another, and the irregular and independent movement of each, always in the direction of its length or altitude, and situate in the interior, as it were, of its body; and also that peculiarity of form which distinguishes these coruscations from all other luminous appearances.

2. The colours of the columns, in that part of their height which is nearest their base, and where, as a ground, they had only the white light of the horizon, by which, and by their motion, and it should, perhaps, be added, their vividness, they were distinguished, is a point upon which the writer speaks with some hesitation, and with respect to the more close observation of which he could like to enjoy a second opportunity of beholding the phenomenon. The variety and richness, and sometimes the terrible grandeur, of the colours [p389] exhibited in the Aurora Borealis, is the constant theme of spectators and naturalists; and, upon the late occasion, an observer, apparently of more regularly scientific habits of pursuit than himself120, has particularly insisted upon a column, of a violet colour, rising west of north, and the place of which he thinks corresponding with that of the magnetic pole; a coincidence from which, as it may seem, he would believe a confirmation of the magnetic theory of the production of the Aurora to be obtained. In setting down the present description, the writer tasks himself to the most faithful description of what he actually saw, and suppression of all desire to support or condemn a theory, of which his mind is capable; and by those rules, therefore, the whole statement will be guided. His description already differs from that of some of his fellow-witnesses, as will be expressly considered below; but he confesses that while, in point of persuasion, he much inclines to the idea, that all the light displayed by the Aurora is in itself white, and only tinctured to the eye of the spectator by the atmospherical medium through which it is seen; and while, with respect to all those deeper colours, whether crimson or purple, or blood-colour, which appal the superstitious, and are described by the picturesque narrator as exhibiting the terrible in matters of vision, he judges it supposable that the whole machinery consists in the same interposition of vapour, near the horizon, which so often gives to the sun and moon themselves the appearance of being coloured like blood: while, therefore, he still adheres to his opinion, that the colours ascribed to the Aurora are wholly extrinsic; and, to borrow the words of a scientific writer, “dependent upon the medium through which they are seen;” he is obliged to acknowledge, that it did appear to him, that the several columns, in truth, were yet variously coloured, of pale, but bright and pleasing colours, from a pale yellow to a pale pink and a pale violet, and this in the direction of their height or length,—a phenomenon which wholly excludes, as to those columns and their colours, the influence of an interposing medium, the effect of which would be perceived horizontally, and across the whole range of columns, or part of the range, and not [p390] vertically nor obliquely, according to the direction of each column, and within the limits of its sides. He confesses, also, that he did take notice of the pale, but bright violet-coloured column, distinguished also by its breadth and height, and situated to the west of north; but which column, he is surely right in adding, ultimately moved, with those next to it, toward the north. He distinctly and pointedly observed, at the same time, that the columns which stood due north were always white, and that the colours of the other columns appeared to strengthen in proportion as they were distant from the due north, either west or east; and he came to a fixed conclusion, while the phenomenon was under his eye, that, to his judgment at least, the strength of the fire, so to say, was in that point of the horizon which lay due north; and that there was a diminished brightness, with a proportionable increase of colour, to the right and left.

3. As to the separate movements of the columns, these, in the first place, were quick, and forced upon the eye, while the movement which gradually deployed or advanced the right wing of the celestial arm, and gradually contracted or withdrew the left, was slow, and perceived only by its results; and, in the second place, while these latter were parallel to the horizon, the former were either vertical, or in the oblique or curved direction of the bodies of the columns. But this motion consisted either in vibration, or in irregular but alternate projections and contractions; and the motion of each column, as has been said, was independent on that of others. Rarely, two adjoining columns were in motion at the same time. Almost always the moving column or columns were seen to start from the midst of others, which, for the time, were quiescent, but which had had their turn before, and would presently have it again. What eminently struck the writer, however, was the internal motion of that to which he cannot allow himself to give another name than that of the apparent luminous material of the columns. It seemed to him as if the volume of each column or coruscation was itself composed of parallel lines of luminous matter, arranged in the direction of the column, and every one of which was separately the subject of movements similar to those of the entire [p391] column, or entire bundle of lines; or as if the whole column were like the stalk of a plant, and filled with upright and luminous fibres, or like a skein of thread, drawn vertically or obliquely, and of which each particular thread should have particular motion in the direction of the whole; or (what he thought the comparison which proclaimed the very nature of the material of the columns) like fountains, or jets of water in the sun, in which every particular particle should be moving in the general direction of the jet, and yet each moving and shining for itself.

4. And this apparent nature of the substance of the columns or coruscations allies itself to what finally regards them; namely, their form. In this description, they have hitherto been spoken of by the name of columns or pillars; and the similitude, which that name suggests, is justified by the general figure of all the lower parts of their bodies, which, unlike the figure of rays of light on the one hand, and unlike that of flames of fire on the other, is a tall or lengthened object, of small comparative diameter or breadth, and of which the sides consist in right and nearly parallel lines. But, by the English, these columns, pillars, or coruscations, were anciently called so many burning spears; and they have also received the names of streamers and pencills121, which two latter, in the history of appurtenants of war, signify long and narrow, and pointed banners or flags. Their similitude to flags is excusably fancied from their quick, capricious, and irregular motions, but their likening to “spears,” is that which may claim to be thought the most felicitous, as to the true conception of their form, as it is also that, the idea of which contributes to render the phenomenon the most fearful in the [p392] survey of ignorance and superstition. But the SPEAR-SHAPE is descriptive, because the coruscations, unlike rays of light, and unlike flames of fire, have neither the obtuse figure of a pyramid, nor the acute one of an obelisk, upright or reversed; but, after rising, through almost their whole height or length, of an equal or nearly equal diameter, terminate in a point which is formed, not of right lines, like the point of a dagger, but of curved lines, so as to form the rounded point of a spear, or that figure which is so familiar to botanists, as spoken of “spear-shaped” leaves. A ray of light, in whatever direction it is thrown, broadens, with right-lined sides, from the first point of its departure, to the furthest stretch of its projection; a flame of fire points uniformly upward, with the same regularity of form, excepting only as it is liable to undulation from the motion of the atmosphere; but, the columns, spears, streamers, or coruscations of the Aurora Borealis, have no form but that under review.

5. About half-past eleven o’clock, or nearer to twelve, several powerful columns shot toward the zenith; while, to the east of north, others were at once curved in their form, and projected in an angle of about thirty degrees with the horizon. But while, upon the west of north, the sky, above the ridge of clouds, was entirely clear, so that, there, the columns played upon a ground which formed a slight contrast with themselves, here, the clouds were still heavy, and the columns behind them appeared, in consequence, of a fiery red, deepening as they approached the outer edge of the whole display, at which was the sharpest outline, contrasted in the distinctest manner with the dark sky. The light upon that side called to the mind of the writer the “dunnest smoke of hell,” of Macbeth; while, as to its outer line, as seen from the east end of Pall-mall, the sides of the stone spire of St. Martin’s church, which rose to the eastward of it in the sky, were not more sharply defined; the dark intervening sky affording relief to both, though not equally so, upon account of the superior brightness of even the obscured columns. But, in taking leave of this columnar, or spear-like, and main part of the Aurora, it may be permitted to add, that, in those tapering forms, together with their motions, (though the comparison [p393] may still be sufficiently remote and fanciful,) it was easy to discern the origin of their having been resembled to weapons of war; that is, to the spears of an army, raised, lowered, laid at angles, and gleaming, glittering, crossing, and clashing in battle. And equally, too, from their quick, varied, and separate, and, as it were, whimsical motions, might they reasonably receive, in their milder displays, and in moments of more peaceful and cheerful association, the very different name of merry dancers!

III. Though, as will presently be found, it is the ruling idea of the present writer, that the Aurora Borealis is a single object, its appearance, when unmodified by the accompaniments of clouds or fogs, being merely that of its own coruscations, playing in the free expanse, yet for the purposes of analytical description and contemplation, it is here thought convenient to divide it into the three parts in which, through the temporary and accidental intervention of the coloured arch before-mentioned, it appeared in the night now in recollection. These three supposititious parts, then, may be understood as follows: first, the arch, belt, or band which was temporarily thrown across the heavens; second, the main body of the coruscations below the arch; and third, the coruscations above it, and in or near the zenith. It is of these only that it remains to speak.

It was not till about midnight that the zenith itself (which, however, formed the southern boundary to this part of the display) became the scene of a class of appearances, differing, indeed, essentially, in their forms, from those in the horizon, but closely connected, as it may be believed, with all the materials, and all the movements, of these latter. The zenith, at that hour, was cloudless, and resplendent with stars, and the air was freshened by a gentle breeze from the south. Between the earth and the stars above, there was no apparent intervening vapour, and nothing, therefore, save that atmospherical fluid which eludes the sight. But, through that medium, if such only it was, coruscations were now continually shooting, of which the appearance was, that it overspread this portion of the vault of heaven with an ever-shaken [p394] sheet of thin, gauzy, white, or yellowish-white, and nebulous, or cloudy matter. To the writer, this superior portion of the Aurora, though not the most lustrous, and, therefore, not the most striking of the whole, was yet by no means the least interesting and inviting to attention; for, here, as its appeared to him, the material and the manner of operation of the meteor were brought nearer to the eye, and exhibited with such a back-ground (the starry heavens) as gave a transparent view of the same matter as that, which, (as he thought,) seen vertically, and in the horizon, appeared comparatively, at least, opaque. The transparent medium, however, above, through which, even when shook or vibrating, and even when whitened with light, the stars were always seen in more or less brightness, was now in continual motion; or, meteoric light or matter was continually, though irregularly, and as it were, playfully shot through it. The illuminated substance (whether the atmospherical fluid, reflecting the light of the meteor, or the luminous body of the meteor itself, but probably the latter) was incessantly discovering itself in different places; now here, now there, now bright, now dim; but far less in a manner, or with an appearance, such to be compared with lightning, than with such as resembled the changes of ripple upon the bosom of a wide-spread water, when a variable breeze blows over it; first in one part, and then in another; and now in one direction, and the next moment in a second. Or, the canopy of heaven, at this time, might be said to be composed of a lace or gauze bearing a figured pattern, of which the fluttering motion continually changed the places, or hid or re-displayed the figures represented; or the picture, perhaps, will be more easily imagined, if conveyed in the very appropriate language of an older hand, which, referring to the appearances displayed in the zenith, remarks, “They break out in places where none were seen before, skimming briskly along the heavens; are suddenly extinguished, and leave behind a uniform dusky track. This, again, is brilliantly illuminated in the same manner, and as suddenly left a dull blank.” It should be understood, however, that, at least as seen by the present writer, in this mixture of white and blue, the blue was always the preponderating colour; or, in other words, [p395] that, the field of the unoccupied zenith always bore a large proportion to the space or spaces covered, however momentarily, with light, or with the luminous substance. For the rest, the particular mentioned in the passage which has now been quoted, namely, that of the residue of a dusky track, after the departure of the white light, did not, if it was there, attract the attention of the present writer, upon the late occasion; but he certainly, in many instances, remarked the return of the light to the places in which it had been visible before; and this feature, either with or without that of the continuance of a dusky track, is possibly capable of adding some support to the general opinion which he conceived at the moment, which all subsequent information has still allowed him to retain, and of which he proposes to make further use; namely, that the appearances in the zenith are only extended exhibitions of the luminous phenomena in the horizon, or their southern extremities, or the tops of columns projected from the northward. He thought that, in the zenith, he saw the same material, parcelled out, attenuated or diluted, spread thin, and, as it were, shown with greater transparency, with that which, in thicker volume, with more accumulated strength, intenser light, with more solid body, and withal behind a denser mass of atmospherical vapour, arose, and glowed, and sometimes gloomed, in the horizon. But, be this as it may, it is, perhaps, this upper part of the exhibition, in which the lights or streamers seem to interweave, or cross and recross each other, to dance in and out of the area, and to indulge in motions still more capricious or anomalous than is probably the real fact; it is, perhaps, this upper part which has alternated, as before recalled to view, the names and similitudes of spears, gleaming, glittering, interposing and clashing as in battle, and of merry dancers, the latter the gayer comparison of the dancing north.

IV. The Aurora continued to fix the attention of the writer till between twelve and one o’clock of the morning of the 26th; and he presumes that it continued visible till the superior light of the rising day eclipsed its glory. The 26th was warm, but oppressed with fog, through which the sun broke [p396] only at intervals; and, between four and five o’clock in the evening, a small but steady rain commenced, and continued, or rather increased in heaviness, till after midnight. Between eleven and twelve, while it still rained, the writer, on looking at the sky, which was covered with a uniform mass of clouds, the writer observed, from point to point, over the northern and southern hemispheres, a glow of ruddy light, which he suspected, and still suspects, to have been produced by the light of the continued Aurora, reflected by the vapour. He took the opinion of a fellow-traveller, which coincided with his own; but it has not come to his knowledge that any individual, himself and his companion excepted, has formed a similar conjecture—nor, indeed, is it impossible that it was no more than the light of the hidden moon. The night of the 27th was star-light, though with fog near the surface; and there was then no appearance of an Aurora. The night of the 28th was remarkably clear, and there was still no return of the Aurora. The morning of the 29th was warm, with continued and heavy rain; but, after this, there succeeded a week or more of clear and dry weather; and these united particulars close the history of the phenomenon, as far as belong to the personal observation of the writer. The direction of the winds, and the state of the barometer and thermometer, were of the same general description, during many days subsequent to the appearance of the Aurora on the 25th, as that which had belonged to them from the 20th, and almost for many days before, and of which the particulars have been stated above; and these remarks may merit record, as connected with the question of the ordinary duration of the Aurora, and of the weather by which it may be thought produced, or which it may be thought to bring. In many instances, it has been observed, even in its splendour, and even in southern latitudes, for several nights in succession; and an influence upon the weather has likewise been expected from its appearance. Upon this occasion, there was no remarkable change in the latter till the night of the fourteenth day after the Aurora (October 10th), when there occurred a violent gale of wind from the south-west, accompanied with loud thunder, and the most vivid lightning; subsequently to which, as usual, [p397] the air, for a few days, was felt to be cooler than before. It has been said, that a gale of wind, from the south-west, is always to be looked for within twenty-four hours after the Aurora.

V. The astronomical writer, already more than once mentioned, speaking of the Aurora of the 25th of September, describes it as “that mysterious phenomenon;” and Mr. Adams, the meteorological correspondent of the publication referred to, records it as, “perhaps, as conspicuous as any that has ever been seen in England122;” so that, assuming these impressions in both instances to be well founded, neither the present state of science upon the one hand, nor the specimen of the phenomenon upon the other, are such as to discourage either of the objects of the remainder of these pages; namely, the one to contribute, as fully as possible, to the completion of a faithful account of the Aurora, as seen in London upon the late occasion, by uniting, and by analysing the descriptions that have caught already the eye of the writer; and the other, to correct, and to enlarge if it should be practicable, the natural history of this description of meteor, by the comparison of what has hitherto been usually written upon the subject, either descriptively or philosophically, as well with the results of the late actual observations, as with the several facts or opinions more anciently registered. According to some, the interval which had elapsed, since an equal or a superior display of this phenomenon was witnessed in London, is twenty-four years, and, according to others, thirty-six; nor is the scanty list of examples scientifically recorded, at all inconsistent, from the wide separation, as well as irregularity of its dates, with such a view of the infrequency and uncertainty of any considerable appearance in other southern latitudes. The opportunity, therefore, now offered, ought not, perhaps, to be neglected; and the writer is not wholly without the prospect, that, upon a re-examination, both of opinions and facts, some safe and inevitable conclusions may be elicited, both as to the history and the theory of the meteor, hitherto, the one hastily received, [p398] and the other negligently overlooked, or unwarrantably contradicted. The paragraphs, then, which immediately follow, will connect and review the accounts of the writer’s fellow-observer of the 25th of September; while those which succeed will be devoted to a brief enumeration of statements already recorded in books; though, to a certain extent, both these paths will involve us in mixed investigations, historical and theoretical.

1. “It first appeared,” says Mr. Adams, who dates from Edmonton, in Middlesex, “about eight o’clock in the evening, as a strong white light, much resembling the approach of sunrise; and so continued till a short time after eleven, when a considerable number of dark clouds collected toward the north and north-west, and several streaks of a pale white light were seen proceeding from the clouds, and reaching nearly to the zenith. But the most remarkable part of the phenomenon was exhibited in a N.N.E. direction, where, at about 30° above the horizon, was a small dense cloud, above which was a broad streak curved, and about 10° in length, varying in colour from a deep copper hue to a red.” “From this,” continues Mr. Adams, “the coruscations were incessant, and remarkably bright, darting frequently to the zenith, where they were frequently crossed by others equally bright and numerous, proceeding from the west toward the east.”

2. The astronomical writer, who dates from Deptford, describes the phenomenon as commencing at a quarter past eight o’clock, and travelling, from west and north-west, to north-east; and the streaks, or streamers, or, as he denominates them, the flashes, “converging to the zenith,” and “coruscating with great velocity.” He also particularises the peculiar appearance of “a streak or column of a phosphorescent violet tinge;” and adds, “The two red beams of light, seen in the easterly and westerly direction [directions], were diametrically opposite to each other, and ninety degrees distant from the violet light (by far the most luminous, though comparatively quiescent) which was to the west of north, and therefore could not be far from the magnetic meridian, which would be crossed at right angles by a line joining the places of the red beams. The southern edges of these were accurately defined, not blending with the adjacent azure, but most distinct from it, and [p399] perpendicular to the horizon.” Finally, this gentleman speaks of the general luminous aspect, as “much resembling the tail of a comet,” and says, that Ursa Major, and other stars, were visible through its medium; that three meteoric stars also appeared, during the phenomenon, in the east and north-east; and that the entire horizon was obscured by dark, heavy clouds, from three to five degrees in height123.

3. Besides these observers, two or three others, if not many more, less scientific, perhaps, but yet entitled to attention, have communicated to different newspapers their accounts of the same phenomena. “The metropolis,” says one of these, “was surprised on Tuesday night by a brilliant display of Northern Lights, which but very seldom stray so far south. The last which we beheld in London were in the autumn of 1804, about the end of September, or beginning of October; and the fancied prodigy filled all the superstitious heads, at the time, with fearful prognostics, and loosened the tongues of a hundred prophets. The spectacle, then, was truly magnificent. On Tuesday night (the 25th) the northern parts of the heavens displayed, about eleven o’clock, so ruddy a blaze, as to appear like the reflection of a mighty conflagration. An hour later, the red hue was gone; but the whole horizon, from the north to the east, was lined with a thin cloud, from which the rays of light rolled, or sudden rays flashed up, and as suddenly vanished, to appear in a different part.” “At about half past eleven o’clock,” says a second, “my attention was attracted to a singular appearance of light and streakiness in the sky. I observed it for nearly two hours. The sky, to the north, was obscured, for about fifteen degrees above the horizon, by a dense stratum of black clouds; from the upper edge of this, the light became first apparent, extending from nearly north-east to north-west, exceeding considerably in power that arising from the moon just previous to its rising. From this broad stratum of pale yellowish light shot beautiful pencils, of a luminous, hazy appearance, up to the very zenith, changing momentarily in length and intensity. During this period, the wind blew gently from the south; and I frequently observed, that when it freshened [p400] a little, the Aurora Borealis became more brilliant in its appearance, sending beautiful coruscations of light, in rapid succession, towards the zenith, and frequently passing that point ten or fifteen degrees to the southward. I have been assured, by those who are well acquainted with this beautiful phenomenon, that they have not seen any appearance of it equal in brilliancy and beauty to this, for upwards of six and thirty years.” “Last night,” says a third, “we were favoured with that interesting phenomenon, the Aurora Borealis, or Northern Twilight, which so often amuses and cheers our neighbours in the north, but seldom, I believe, is seen in our latitude. It was without those varied colours,” adds this writer, “which cause it to be a grand spectacle in those regions.” “Not far from the horizon,” he adds, “in the northern hemisphere, were transparent bodies of light, eclipsing the brightness of the stars, which, however, were perceptible through it. From hence, beams of light, varying in degrees of brightness and breadth, shot up towards the zenith; here streamers of light flew from the east to the west, and from west to east. The southern hemisphere was cloudless, the stars shining with brilliancy. By the light of this phenomenon, I could discern the time of night, which was between eleven and twelve, as well as other objects, as they appear on a moon-light night, when the moon is obscured by clouds.” “The sky in the north,” we are told by the fourth, “appeared as if a light shone from behind some dark masses of clouds. As I approached Hampstead, the silvery light was gradually tinged with rosy spiral streams, like those which sometimes precede the rising and follow the setting sun. These spiral red streaks did not appear to move quickly; but they were subsequently followed by the merry dancers, which fully maintained the character bestowed upon them by our northern neighbours. After passing through Hampstead, I crossed the heath, and came down what is called North-end Hill, to Golder’s Green, Hendon. When you arrive at the foot of the hill, you enter upon the open part of Golder’s Green, where you have a clear and unobstructed view of the sky from west to north. I never shall forget the grandeur of the scene which awaited me there. A continuous border of dark cloud skirted the horizon completely from west to north, whilst [p401] from behind it, incessantly and rapidly shot up the most beautiful coruscations of white light, which, being relieved by the dark border, added double brilliancy to the ever-shifting scene.”

VI. But, after transcribing these respective accounts, it may be permitted, for the purpose of uniting them with that submitted in the preceding pages, to remark,

1. That the account by Mr, Adams, of the appearance worn by the Aurora at an early hour in the evening, is, no doubt, entirely correct; and that it is easy to understand, from this description of that early appearance, why little observation was attracted to the phenomenon till about eleven o’clock at night, the time assigned, as well in this, as in all the other accounts, for the commencement of the phenomenon.

2. That the “streaks of a pale white light,” which Mr. Adams describes as proceeding, a short time after eleven, “from the clouds,” must be understood, as stated by the writer last quoted, as proceeding “from behind the clouds;” that, when the astronomical writer at Deptford speaks of Ursa Major and other stars being seen through the Aurora, it must be recollected, that, perhaps, this remark should apply to the medium of the thin and shifting lights in or near the zenith; and,

3. That it is with respect to the “broad streak, curved,” of Mr. Adams; the “two red beams of light,” of the astronomical observer at Deptford; and the “arch” of the present description, that the principal, if not only discordance obtains. Neither of the other three writers appears to have seen any thing, whether of one “broad streak, curved,” and “varying in colour from a deep copper hue to a red,” or of “two red beams,” as spoken by the writer at Deptford; while, in each of the three accounts in which that part of the phenomenon is actually referred to, the descriptions are materially dissimilar:—

1. The writer at Edmonton mentions only a single streak, while the writer at Deptford speaks of two.

2. The writer at Edmonton describes his single streak as curved, while the writer at Deptford says nothing of curvature; and, in describing the position of the beams as “perpendicular to the horizon,” may seem to leave no curvature to be understood. [p402]

3. The writer at Edmonton seems to lift his “broad curved streak” much above the horizon; for he first places a small dense cloud 30° above the horizon, and, then, his broad streak above the cloud; thus describing a curve of which the situation was near the zenith, while the writer at Deptford is describing “two red beams,” standing perpendicularly to the horizon.

4. The writer at Edmonton places his “broad streak, curved,” “in a N.N.E. direction;” while the writer at Deptford records “two red beams of light, seen in the easterly and westerly direction.” Lastly,

5. The writer at Edmonton seems to make coruscations, “incessant and remarkably bright,” dart from his “broad streak, curved;” while the writer at Deptford seems only anxious to place his “two red beams,” as perpendicular pillars, standing on either side of the magnetic meridian.

VII. And, from the whole of this, from the total silence of four accounts, and from the extreme discordance of the other three, the present writer presumes to draw the following inferences, including that of the accuracy of his own original statement:

1. That the two perpendicular red beams of light, of the writer at Deptford, should be joined with broad curved streaks of a deep copper, or red hue, of the writer at Edmonton, to complete the arch which has been spoken of in the foregoing pages.

2. That this arch, or curved streak, with its feet east and west, sent forth no coruscations itself; but that the coruscations rose beneath it, and passed above it.

3. That it was described upon the clouds only; was no part of the Aurora; and, from its connexion with the clouds only, had an evanescence which, on the one hand, was the cause of the various descriptions, and, on the other, of no descriptions at all. The present writer observed this part of the phenomenon from its beginning to its ending. He saw it rise in the west, extend itself from the north, and descend in the east; and he thinks it reasonable to ascribe the variations concerning it, in the coincident narratives, to the different points of time to which alone they really refer. The writers at Edmonton [p403] and Deptford seem to have had their attention fixed upon it at different epochs of its progress; and all the four other writers, who have been cited, seem to speak of a time subsequent to its disappearance. The present writer does not recollect the small cloud below it, spoken of by Mr. Adams; but he well remembers the clouds above it, and along and near the northern edge of which it seems to be formed. He does not recollect seeing its definite southern outline contrasted with the azure sky; but he well remembers seeing that outline contrasted with the dark clouds above it, or to its southward; and also the contrast of its definite, northern outline, as contrasted with the azure sky beneath.

VIII. It is necessary to take notice, also, of what is said above, by the astronomical observer at Deptford, as to the “flashes converging to the zenith,” and, further, of the omission, both by this writer and by Mr. Adams, to speak of the curved beam, streamer, or coruscation, to the east of north, as described above. The whole veracity of the foregoing description depends upon the denial of a uniform convergence of the streamers, pillars, columns, or coruscations toward the zenith; nor was it, in all probability, the intention of the writer at Deptford, to assert any such convergence, but only to speak of those coruscations, or shifting lights, in the zenith, which are described by Mr. Adams as crossing each other from east to west. It is remarkable, at the same time, that neither the one nor the other of these writers have mentioned that direct reverse of convergence which marked the general figure and arrangement of the streamers or columns of the Aurora, and which was so opposite to what would have been given to it by the phenomenon of convergence. Indeed, the violent curve of the extreme column to the N. E. or N. N. E., shrouded, too, as that column was with a body of dense vapour through which its light appeared of a deep and dull red colour, might make the description of this itself answer to the “broad streak, curved,” of Mr. Adams, if we were not certain, from other particulars mentioned, that Mr. Adams really refers to the curve which formed part of the arch. For the rest, no mention of the real directions of the several columns having been made by any observer of the Aurora of the 25th [p404] of September but himself, and especially none of the outward curve of the easternmost column, it is satisfactory to the writer to have found an account of an appearance similar to this last, in an Aurora of which he will presently have occasion to speak.

IX. Finally, there is an observation to be made upon that part of the description, by the second correspondent of the newspapers, where it is said, that during the appearance of the coruscations in the zenith, “the wind blew gently from the south,” and the spectator “frequently observed, that when it freshened a little, the Aurora Borealis became more brilliant in its appearance;” to which it may also seem the writer’s intention to add,—“sending beautiful coruscations of light, in rapid succession toward the zenith, and frequently passing that point, ten or fifteen degrees to the southward.” Now the reality of any dependence of the light and motion of the Aurora upon the freshening of the breeze, would seem too strongly to affect the question of the nature and action of the auroral matter, to be admitted without cautious examination. In truth, what was it that constituted the luminous matter which we saw in the zenith? The stars were visible through it. But for luminous appearances that flew or skimmed along the heavens, we should have said, that the latter were clear, and that there was nothing but the purest atmosphere between the earth and the heavens. Was it, then, the atmospherical matter which was thus illuminated, and which, being ruffled by the breeze, can be supposed to have really exhibited the appearances described by this writer, or, was it not, rather, illuminated auroral matter, which was shot through the atmosphere; and, if this last, how are we to understand that its brilliance, and still less the frequency and vigour of its coruscations, could have been affected by the freshening of the breeze?

X. But, taking, now, a final leave of the description of the Aurora of the 25th of September, and of the observations specially suggested by it, let us here examine the several particulars which are commonly offered as part, at least, of its true history; an undertaking, for the greater convenience of which the account given in a modern work of much and [p405] deserved reputation, shall be quoted and considered sentence by sentence, as follows:

1. “AURORA BOREALIS, Northern Light, or Streamers; a kind of meteor, appearing in the Northern part of the heavens, mostly in the winter time, and in frosty weather.

2. “It is in the Arctic regions that it appears in perfection, particularly during the solstice.

3. “In the Shetland Islands, the Merry Dancers, as they are called, are the constant attendants of clear evenings, and prove great reliefs amidst the gloom of the long winter nights.

4. “They commonly appear at twilight, near the horizon, of a dun colour, approaching to yellow; sometimes continuing in that state, for several hours, without any sensible motion, after which they break out into streams of stronger light, spreading into columns, and altering slowly into ten thousand different shapes, varying their colours from all the tints of yellow to the obscurest russet.

5. “They often cover the whole hemisphere, and then make the most brilliant appearance.

6. “Their motions, at these times, are most amazingly quick, and they astonish the spectators with the rapid change of their form.

7. “They break out in places where none were seen before, skimming briskly along the heavens; are suddenly extinguished, and leave behind a uniform dusky track.

8. “This again is brilliantly illuminated in the same manner, and as suddenly left a dull blank.

9. “In certain nights, they assume the appearance of vast columns; on one side of the deepest yellow, on the other, declining away till it becomes undistinguished from the sky.

10. “They have generally a tremulous motion from end to end, which continues till the whole vanishes.

11. “In a word, we, who only see the extremities of these northern phenomena, have but a faint idea of their splendour and their motions.

12. “According to the state of the atmosphere, they differ in colour.

13. “They often put on the colour of blood, and then make a most dreadful appearance124.” [p406]

1. Now, with respect to the first and second of the sentences here transcribed, there seems reason to doubt the accuracy of the account which almost limits the appearances of the Aurora to the “winter time,” to “frosty weather,” and especially to the winter “solstice.” The frequency with which the season approaching to Christmas, or that of the winter solstice, is distinguished by the occurrence of weather peculiarly mild, insomuch that, almost every year, the period is marked by observations upon what is annually called the extraordinary and unseasonable genialness of the weather, cowslips blooming, leaves budding, and birds building their nests; this frequency of a mild temperature of the air about the period of the winter solstice, may justify, even under a general view, a doubt of the accuracy with which, as things of course, the winter solstice, and frosty weather, are spoken of as arriving in conjunction. But, that the appearance of the Aurora Borealis is not peculiar, either to the occurrence of frosty weather, or to the period of the winter solstice, whether the two latter phenomena are related or otherwise, seems probable, as well from the mildness of the weather at the late appearance, as from the various seasons of the year in which the few others described in our books are recorded to have presented themselves. The earliest mentioned was seen in London in the year 1560, on the 30th day of January. The next was in 1564, on the 7th of October. The next, in 1574, on the 14th and 15th of November. The two next, observed in Brabant, in 1575, on the 25th of February, and 28th of September. The next, at Wurtemburg, as we are assured by Meestlin, seven times, in the year 1580. The next, in an extraordinary manner, in the months of April and September, 1581; and in a less degree, at some other places, in the same year. The next, observed all over France, in 1621, on the 2nd of September. The next in 1707,and 1708, during which two years the Aurora was witnessed five times. The next, in the month of March, in 1715–16. The next, in 1737, on the 16th of December; that seen in London in 1791, of the month of which the writer is uninformed; another in 1803, or 1804, at the latter of September, or the beginning of October; and this, of 1827, on the 25th of September. But, from these statements, it is now seen, that, [p407] exclusive of appearances of the Aurora in respect of which the month is not particularised, eight of the different months of the year occur by name; that is to say, the months of September, October, November, and December, January, February, March, and April; leaving only four months (May, June, July, and August, the identical summer-months of the Polar regions, or months during which the sun visits the Polar horizon!) hitherto undistinguished by the phenomenon of the Aurora, and almost establishing, as the season of its occurrence, not the middle point of the winter solstice, but the whole period extending, in general terms, from the autumnal equinox to the vernal, beginning at or before the first, and ending at or after the last; or, what may be called the entire winter of the northern hemisphere, or the period during which the sun’s course is to the southward of the tropic of Cancer; a deduction from the scanty data offered by such archives of the phenomenon as we possess, not, perhaps, of trifling importance toward the establishment of the true theory of the cause, as well as of the purpose of its being.

2. The third sentence, where it describes the Aurora Borealis as the constant attendant of clear evenings in the Shetland Islands, and thereby a great relief to the gloom of the long winter-nights, is probably tainted with errors in regard to the phenomenon, such as affect its whole history and philosophy. The suggestion has just been hazarded above, that at least considerable displays of the Aurora are probably almost as rare, even in the Arctic regions, as in climates further south; and the truth of this persuasion, as the writer anticipates, will fully appear below. In the sentence now referred to, the word “constant” should, at least, give way to “frequent,” if not to “often;” and a distinction should be allowed for, between those feeble appearances which alone, it may be suspected, are even often beheld in the Shetland Islands, and those extraordinary displays which make themselves visible to their southward.

3. The fourth of the above sentences, in which the Aurora is said to appear commonly at twilight, will have been seen to agree with the time assigned for the commencement of the Aurora in the late example; and this, when coupled with the [p408] observation in the third, that, in the Shetland Islands, it is the constant attendant of clear evenings, will seem to suggest, what, indeed, will probably be easily agreed to, that the Aurora, in itself, is peculiar neither to clear evenings nor to evenings at all; but is in activity during the twenty-four hours, or without intermission; though, to be visible to human eyes, first, the atmosphere must be dark, and, secondly, it must be more or less clear. It may also be thought apparent, from the terms of the twelfth and thirteenth sentences, that too much has not been said by the present writer, of the degree in which the peculiar spectacle, upon each separate occasion, depends, not alone of the proper and really uniform features of the Aurora itself, but also of the atmosphere through which it is seen, with the appearance of which its own appearance is combined; and of the consequent value of a careful separation of the real phenomena of the Aurora, from the adventitious phenomena of the intervening and surrounding atmosphere. That the colours which, whether visibly connected with the atmosphere or otherwise, are displayed during the appearance of the Aurora Borealis, are wholly derived from the atmospherical medium through which we behold it, and that the Aurora itself exhibits only a pure white light, is what the writer greatly inclines to suspect, and what may seem to be rendered still more credible by that which is reported by those who have obtained a partial glimpse of the Aurora Australis, or corresponding phenomenon of the south. This is described, by Mr. Forster, who sailed round the world with Captain Cook, as consisting in “long columns of clear white light;” but the whiteness, in the eyes of the narrator, seemed to establish a difference, instead of a similitude, between the Auroræ Australis and Borealis, Mr. F. wholly overlooking the explanation which his own account supplies! “These columns,” says he, “though in most respects similar to the Northern Lights (Aurora Borealis) of our hemisphere, yet differed from them in being always of a whitish colour, whereas ours assume various tints, especially those of a fiery or purple hue. The sky was generally clear when they appeared, and the air sharp and cold, the thermometer standing at the freezing point.” Now this text is its own commentary. The [p409] Aurora could not have been seen if the sky had not been more or less clear. But the sky was very clear; and this because the weather was severely frosty. The thermometer “was standing at the freezing point.” The weather was settled frosty, and therefore settled clear; for the Aurora appeared for “several following nights.” The atmosphere, therefore, was clear; there was neither cloud nor fog, and thence the whiteness of the Aurora. But these views of the Aurora Australis were partial occurrences, and were characterised, as we must conclude, by the state of the atmosphere at a particular conjuncture, or at a particular season of the year. In point of fact, the Aurora was seen on the 16th of February, 1773, in latitude 58° S. This was the beginning of the Australian winter, and it might be a very cold, and therefore a very clear beginning. But the atmosphere of the southern half of the globe is not always thus translucent; and when it is otherwise, we may depend upon it that the columns of its Aurora “assume various colours; especially those of a fiery and purple hue,” more or less like our own. A friend of the present writer was in the same latitude (58° 12′ S.) in the month of March, a few years since; and, upon asking that gentleman whether he had ever beheld an Aurora in the Southern Hemisphere, his answer was in the negative. The season of his visit, however, was a month later in the southern winter than the visit of Messrs. Cook and Forster; the weather was thick and sleety; it was unfavourable to any view of an Aurora at all; but, had the phenomenon happened to present itself, its appearance, we may believe, would not have presented that of a uniform, clear, white light.

4. In the fourth and sixth sentences, what is said of “change of shape,” and “change of form,” is of a nature exceedingly to mislead such as, never having themselves witnessed the phenomenon, may desire either to figure it to their imagination, or to reason upon its appearances. In reality, there is no such change of shape or form as the words naturally suggest to our ideas; the forms, under all changes, are still linear; and the actual changes, as to form, are limited to such changes only as can be produced with the single material of lines, lengthened, shortened, varied in their direction, and now fixed, now shaken, now darting; and now joined in rapid and intermingling motion. [p410] Add, that these lines are luminous, and varied in colour from white to yellow, red, and crimson, and, sometimes, perhaps, to purple and to violet; that they play, in the lower heavens in a field of light, and in the upper over a sky of blue; and the picture of the Aurora Borealis is well nigh complete. The observation in the ninth sentence, that the vast columns, of which, upon some occasions, the Aurora displays the forms, are of a deep yellow upon one side, which, upon the other, fades gradually into that of the sky, is to be understood, as expressing, that, as in the late example, the outer edges of the columns, or those next the dark or unillumined portion of the horizon, are sharp and strongly defined; while the inner ones are less distinguished from the general field of light in which they stand; and which distinction, after all, is but a delusion of the eye, which more readily distinguishes the variation of colour in the outer edge, which is so strongly relieved by the dark and colder-coloured part of the sky, than the colour of the inner part and edge of the column, which, more or less, approaches that of the ground behind it.

5. Sentences seven and eight appear to the present writer to convey the most accurate description possible, of the appearance of the Aurora in the zenith. The “dusky track,” which remains after the lights which have enlivened it are extinguished, and in which they are so often seen again, may seem to attest the justice of his opinion, that these appearances in the zenith are no other than the far-projected tops of the columns which have their bases in, or rather below, the horizon; tops which, while they fill the southern half of the zenith, to the view of spectators under our parallel, must gradually descend toward the horizon, in the eyes of such as behold them further and still further to the south; till, like the topmast of a receding ship, they first scarcely remain discoverable above the convexity of the surface intervening, and finally dip and sink beneath it. But, upon this assumption, the appearance, and therefore office, of the Aurora Borealis, must be conceived as extending far to the southward of even our own island; and the statement, as in the eleventh sentence, becomes more or less inaccurate, that “only the extremities of these northern phenomena” are witnessed by ourselves. In reality we are [p411] ourselves inhabitants of the Northern hemisphere; and the relationship of the Aurora to the wants of the whole hemisphere is more extended, perhaps, than we have commonly imagined. It is even a contradiction to say, as in the eleventh sentence, that we see only the extremities, that is, the Southern extremities of these Northern phenomena, after having said, in the fifth sentence, that “they often cover the whole heavens, and then make the most brilliant appearance;” unless, indeed, in both of these remarks reference is made to the spectacle beheld under more Northerly parallels, a reference which is further suggested, together with their apparent origin, in the terms of a description by Gmelin, to be cited below, of the Aurora as beheld upon the coasts of the Icy Sea; If the Aurora, there, or upon the banks of the Lena or Yenesei, is seen to rise in the north, but yet to stretch itself over the whole hemisphere, it must follow, that its “extremities,” that is, its southern extremities, so far from being all that is seen in these situations, are really projected, on those occasions, so far to the southward, as to escape the ken of our northern optics; a fact of which the explanation must be familiar, inasmuch as, owing to the convexity of the surface of the globe, the horizon of every part is narrowly bounded, whether upon the South or upon the North; whence it results, that any celestial, or even atmospherical appearance, stretching only a little way beyond us to the Southward, or toward the East, or toward the West, must soon reach the horizon upon either of those sides, and thus cover all that, to the eye of any individual, is visible of the “whole hemisphere.”

6. But the description, by Gmelin, of the Aurora, as seen upon the shores of the Icy Sea, and more than all, the simplicity with which the naturalist is disposed to fix its birth-place in that precise interval of the earth’s surface which divides the mouth of the river Yenesei from that of the river Lena, in the North-east of Asia, (a spot so far to the North-eastward, too, of our own!) while it may possibly explain the origin or bearing of remarks, that it “sometimes covers the whole hemisphere, and then makes the most brilliant appearance,” will also afford something of an answer to such as, with the writer quoted above, seeking to connect the Aurora Borealis with the [p412] Magnetic Pole, would discover its same birth-place, or focus, in the North-west, or nearer to the North-west of America, than to the North-east of Asia! It may furnish a reply, also, to Gmelin himself, who, though he tells us that, even upon the banks of the Lena and Yenesei, the Aurora is still seen to rise to the North or North-east of those situations, yet imagines those very banks to be its “real birth-place;” for is it not plain, in the meantime, and this from the very statement of the author, that, travel as far northward, or north-eastward, as we will, the birth-place of the Aurora still retires from our feet; that, even upon the shores of the Icy Sea, the joyous phantom is still to our Northward, or North-east, and that we may reasonably conclude, that even a voyage upon that sea would not carry us to the cradle in pursuit; that, in short, at the North Pole, we should still behold it rise in the North, or the North-east, or the North-west; that we might sail down the Western Hemisphere, and yet only discover, that the Aurora was now in the North behind our backs, as it had been before in the North before our faces; and that, in short, so long as we do but admit its existence in the North, the particular soil or sea is best described in the most general terms:—

The search, too, for the paternal hearth of the Aurora Borealis in any particular division of the Northern Hemisphere, and especially the attempt to find it at the Magnetic or Electric Pole, is, perhaps, so much the more hopeless, after ascertaining, as above, that each hemisphere has its Aurora; and after concluding, as we may have been led to conclude with reason, that each Aurora, other things equal, resembles the other! What is remarkable, also, is that, in the Southern Hemisphere, as well as, according to Gmelin, in the Northern, it is to the Eastward, or to the East of North, that the Aurora has its apparent focus. “A beautiful phenomenon,” says Mr. Forster, (Feb. 17, 1773, lat. 58° S.) “had been observed during the preceding night, which appeared again this and several following nights. It consisted of long columns of white light, shooting up from the horizon to the eastward, almost to the zenith, and gradually spreading over the whole southern part of the sky. These columns are gradually bent sideways [p413] at their upper extremities; and, though in most respects similar to the Northern Lights (Aurora Borealis) of our hemisphere, yet differed from them in being always of a whitish colour; whereas ours assume various colours, especially these of a fiery or purple-hue. The sky was generally clear when they appeared, and the air sharp and cold; the thermometer standing at the freezing point.” This occasional bending of the columns, “sideways at their upper extremities,” instead of uniform convergence toward the zenith, observed by Mr. Forster in the Aurora of the South, is plainly the same peculiarity which was recently witnessed in London, in the Aurora of the North, and a circumstance which, in whatever way explained, assists in the identification of the natures of the two phenomena; and, if we are still to hesitate, upon account of the whiter light of that of the South, let us believe that particular to originate in some peculiar constitution of the Southern atmosphere, from which, in one way or another, not here to be discussed, the cause of the difference may offer itself. But Gmelin’s account of the Aurora of the North, to which the attention of the reader has already been called, is that which is here required to follow. It is to serve to illustrate, as will be remembered, much of the foregoing: “This Northern Light,” says that author, “begins with the rising of single light pillars in the North, and almost at the same time in the North-east, which, gradually increasing, fill a large space in the heavens, rush about, from place to place, with incredible velocity, and finally almost cover the whole sky, up to the zenith: the streams are then seen meeting together in the zenith, where they produce an appearance as if a vast tent was expanded in the heavens, glittering with gold, rubies, and sapphires. A more beautiful spectacle cannot be described; but whoever should witness such a Northern Light for the first time, could not behold it without terror; for, however beautiful the illumination may be, it is attended, as I have learned from the relation of many persons, with a hissing, crackling, and rushing noise, throughout the air, as if the largest fireworks were playing off. To describe what they then hear, they make use of the expression, ‘Spolochi chodjat;’ that is, ‘The furious army is passing!’ The hunters, who, upon the confines of the [p414] Icy Sea, follow the chase of the blue and white foxes, are often overtaken in their excursions by the Northern Light; and, upon this occurrence, their dogs are so much frightened, that they will not move, but cower obstinately upon the ground till the noise is over. The weather, after the appearance of the Northern Light, is usually clear and calm. I have heard these accounts, not from one person only, but from many of those who have spent several years in these very Northerly regions, and inhabited different countries from the Yenesei to the Lena, so that no doubt of its truth can remain; for here seems to be the real birth-place of the Aurora Borealis.”

8. Upon this statement itself, it is only needful to remark, that the rising of the pillars in the North-east, or to the East of North, rather than to the North-west, or West of North, almost at the same time with their first appearance in the North, is not, perhaps, even as seen between the Lena and Yenesei, so uniformly the case as M. Gmelin may have been led to believe; and that, at all events, as above described, the progress of the late display, observed in London, was, first from North to West, and afterward from West to East; the North being always the centre, or always light, while the West and East were changed. The covering of the whole sky, and the splendour of the scene produced, have been the subject of previous remark; and the observation, “that the streams (previously called pillars) are then seen meeting together in the zenith,” entirely corroborates what the present writer has said of the nature of the lights seen skimming across the zenith, and across each other, and the deduction which he has thence made, that the luminous appearances in the zenith are the summits of those very pillars of which the bases are on or below the horizon. The clear and calm weather which, on the shores of the Icy Sea, commonly follows the appearance of the Aurora is, in some degree, in concord with the phenomena of its recent appearance in London; where, without any material change in the temperature, a succession of clear, calm, and bright days supervened, within a day or two of the Aurora. As to the hissing, crackling, or rushing noise, which is said to accompany the Aurora in the more northern regions, and which has sometimes been compared to that of the furling and [p415] unfurling of flags, there is nothing difficult, (knowing what we do of the noise of winds and of thunder,) in admitting its probability, unless what may arise from the consideration, that the noise might, or might not, be expected to be heard, where-ever the phenomenon is to be seen. But the most striking and important truth, communicated in the foregoing account, is that which we cannot but rigorously infer from the collective testimony of two very distinct descriptions, which is afforded in two of the concluding sentences. It consists in that real infrequency, as well in the Northern, as in the Southern Hemisphere, of the appearance of the Aurora; an infrequency the knowledge of which is so essential to the true history of the phenomenon, and therefore to its true philosophy, and consequently to much of the history and philosophy of nature at large;—an infrequency which the present writer has given notice of above, as a proposition for which, in dissent from all received authorities, he will contend; and upon the opposite account of which matter, in the general account quoted, he has already requested the reader to suspend his judgment. It is obvious that, as a natural phenomenon, an Aurora Borealis, which, though constantly experienced in the more Northerly regions, is but rarely observed in the more Southern; that is, an Aurora Borealis which, though familiar to the Samoiede, the Laplander, and even the Shetlander, is an extraordinary, and a terrific, or at least a marvellous event, to the Italian, the Frenchman, and even to the Englishman; it is obvious, that such an Aurora Borealis, constant in its occurrence a little further to the Northward, and almost the solitary spectacle of a generation a little further to the South, is, as a natural phenomenon, a very different thing from an Aurora Borealis which, though far enough to the South, sufficiently frequent in comparatively trivial magnitudes and lustre, is seen, either in the South or in the North, in its greatness, and in its splendour, but yet rarely, and with, perhaps, almost equal rareness; it is obvious that, as natural phenomena, and not less so as sights connected by mankind with their own fortunes, the two things now described are exceedingly unlike as matter of history, and equally so as matter of philosophy. If we are simply to record the occurrence, it is one thing to speak of a phenomenon [p416] which, in the South, is seen only at long intervals, while it is a “constant attendant” in the North; and another thing to speak of that which, whether in the South or in the North, is equally rare, and equally out of the “constant” course of nature. If we are to write the history of nature, it is one thing to relate, that such phenomena, or rather others, infinitely more splendid, more terrific, or more marvellous, than that which was witnessed in London, in the month of September in this year, or in the same month some three-and-twenty years ago, or else some six-and-thirty, and, to judge by experience, is not to be looked for, in the same city, during twenty or thirty years again;—it is one thing to relate that, in the Shetland Islands, such a spectacle is a “constant attendant of clear evenings,” and another thing to relate, that though, perhaps, on clear evenings, in the Shetland Islands, some small displays of the Aurora are not unfrequently perceived, yet, that such an exhibition as has recently been witnessed in London, and still more, such as, more effulgent, and more extended, and more vigorous, and even coloured by the atmosphere into the terrific;—that those exhibitions, in short, of which our naturalists and men of science would persuade us, that, while beheld nightly by those of the North, they are known to us by very faint examples alone;—those exhibitions,—that those extraordinary examples of the brightness and vigour of the Aurora—are as rare, or almost as rare, not only in the Shetland Islands, but in Iceland, and on the shores of the Icy Sea, as in the streets of London themselves! It is obvious, too, that if we are to speak of this phenomenon philosophically, if we are to attempt to explain its origin and use,—its source in the natural elements, and its office in the natural economy; here, too, the solving of this question of the frequency or infrequency, the constancy or the inconstancy, of these mighty exhibitions, even in the North, and under the Pole itself, is matter of foremost importance. And what is the testimony, upon these heads, which is borne by the accounts collected by Gmelin? Is the Northern Light of the German naturalist, the apparently constant attendant of clear evenings, even in the countries between the Lena and the Yenesei? Is the spectacle, and the atmospherical hurley, which seems to rush over the [p417] hunting-grounds of the hunters and their dogs, and which frightens the very dogs, and pins them to the ground till it is passed, or has seemed to pass; is this the “constant attendant of clear evenings,” or, is it a prodigy so uncommon as to defy familiarity? But, if this evidence is insufficient, let us look to what is said of its influence, in these countries, on the subsequent state of the atmosphere. So far from the Aurora being an attendant or follower of clear evenings, it seems that clear evenings follow the Aurora! It is said, that after its occurrence, clear and calm weather is customary to follow; and, here, the expression itself is implicative of the rarity of the occurrence. If it were constant, how should this result come to be noticed; and, indeed, if the Aurora Borealis were the constant attendant of each twenty-four hours, and if clear weather were usually in the train of the Aurora Borealis, how could it ordinarily happen, that there should be any thing else than clear weather, in the countries visited by the Aurora, or any foul weather for the Aurora to dispel? Yet, such is the established prejudice concerning this supposed frequency of the more powerful displays of the Aurora in the climates further to the North than our own, that a writer, quoting the very statement above, absolutely prefaces it with the remark, that Gmelin, in pointed terms, speaks of the Aurora as “frequent,” as well as “very loud,” “in the North-eastern parts of Siberia125!” A simple perusal, in the meantime, is sufficient to show, that Gmelin says nothing affirmative as to its frequency; while a slight consideration of the facts which he adduces must satisfy us, as no doubt they satisfied Gmelin himself, that the occurrence, even in Siberia, is actually infrequent!

XI. In reference, however, as well to the image presented above, of “a vast tent expanded in the heavens, glittering with gold, rubies, and sapphires;” as also to many less ambitious and figurative descriptions of the spectacle of the Aurora Borealis, (not excepting that indicted by himself,) the author is anxious to suggest a caution against the too exaggerated conception of the realities intended. Words, [p418] upon such occasions, are rarely more than imperfect pictures, presenting but feeble likenesses, and either deficient or excessive in the amount of beauty, or of the reverse, of whatever kind, which they attempt to copy from their originals; and the inconvenience is seriously great, whenever the object portrayed is wholly strange to the mind before which it is placed. The imperfect power, both of words and written characters, to convey precise, and sometimes even tolerable ideas, of the objects, either sensible or abstract, which they are intended to represent, and the superior intelligibility so often belonging to diagrams or figures, or other resources of the art of drawing, (the primitive, and, for so many purposes, the most instructive mode of writing126,) would have led the present writer, had time permitted, to endeavour, as often as possible, to elucidate by such means the several parts of the foregoing observations; but which means, at last, and in reference to the actual phenomena of the Aurora, would necessarily fail to convey the due, and yet no more than the due impression, to such as are wholly without its ocular acquaintance. We are little aware how much, upon ordinary occasions, our understanding of words heard or read is assisted by our previous knowledge of the sensible objects, or of the acquired notions, to which they refer; and the examples would be endless, of the sensible objects preposterously misconceived, as well as the propositions made false or ridiculous, through the frequent inadequacy of words to communicate truths entirely new [p419] to the disciple. Even the history of opinions concerning the Aurora Borealis itself, might be cited upon this very point.

The ordinary and natural resource, in such circumstances, is comparison; but even comparison has been the source of great and endless errors of description. Of the degree of resemblance proposed between the known and the unknown, there is no common measure for the minds of the hearer and the listener, and the point or points of comparison intended by the first must often be mistaken by the second; or, if reference is made to a similitude under one aspect, the imagination conceives a resemblance also under another: thus, if it is said, that an unknown animal is as large as a horse, the idea of the figure also of a horse, is apt to be attached. A modern English work of science premises, upon the subject of the Aurora Borealis, that its appearance is so well known as to render description needless. It is true that the work referred to is printed in the Northern part of the island, where the phenomenon is doubtless more familiar than in the Southern; but, in the foregoing pages themselves, it has, perhaps, been demonstrated as probably certain, that if it is any where sufficiently known to render description trite for the common eye, it has at least never hitherto been described with sufficient precision for the aid of speculative research. To attempt to explain its cause, and to relate its entire history, its appearance must first be either observed or described with accuracy; and we have seen, above, that some of the most scientific reasonings which have hitherto been offered as to the former, are wholly inapplicable to the true peculiarities of the latter.

Considered simply as a visual object, and as a meteor differing from all others, and especially from all other luminous meteors, in this, that its duration extends to hours, if not to days and months; the only resemblance, perhaps, that can be suggested, is to that description of lightning which is called heat-lightning, the frequent companion of our summer-evenings. But, here, the similitude is inexpressibly feeble; since heat-lightning has nothing, either of the splendour, the volume, or the beauty of the Aurora; and since the light of the latter, however mobile, varied, and, from time to time, increased and diminished in itself, is yet, as to general effect, continuous and [p420] steady. There remains, then, but to compare the phenomenon of the Aurora with the rising or the setting Sun. In both of these latter, as in the Aurora, the light is in the horizon, and that light is shot upward, perpendicularly, or obliquely, toward the zenith or toward the right and left; and both of these, like the Aurora, are more or less constantly attended with a variety of colouring, similar in hue if not in depth, and always beautiful, and often gorgeous. With the Sun, and with the beams of the Sun, ancient description, in point of fact, has confounded the Aurora Borealis, to the degree, perhaps, of giving origin to some of the ancient and poetical descriptions of the Sun, utterly inappropriate and inexplicable as understood of that day-star, but easily recognised in the Aurora; yet the dissimilitudes, at last, are numerous and great! Of the essential difference of figure, both as to the beams of the Sun, and the beams of the Aurora, in severalty, and of the inevitable difference of indication of which, as to their nature, mention has been already made; and also as to the general or collective figure of the beams of the Aurora, as contrasted with that of the rising, or of the setting Sun. The next point is the homogeneity of colour in the beams of the Sun, however the apparent colour may vary, as it is seen to do, from horizontal stratum to horizontal stratum, from the horizon to the zenith, according to the varied density of the medium between the light and the eye of the spectator. The light, upon the other hand, of the beams of the Aurora is heterogeneously coloured in itself, and is so displayed; and not, therefore, varied as the beams ascend from horizontal stratum to horizontal stratum, or as crossing all the beams together, but found in each particular beam itself, and attending its direction, whether vertical or inclined, and whether rectilinear or curved. Waiving, then, any comparison in detail, between the phenomena of the Aurora, and the phenomena of the rising or of the setting Sun, but admitting that, to a certain degree, all are alike vast in dimensions, splendid in light, rich in colour, and durable upon the eye; there is still nothing else to be subjoined, than that, at least with reference to vastness of dimension and magnitude of the volume of light; to the quantity of light diffused; and to the richness and gorgeousness of [p421] the attendant colouring; there can be little risk, in the assertion that, vast, and splendid, and beautiful, and rich, and gorgeous, as, when seen in the most favourable situation, and under the most favourable circumstances, the Aurora may be, it is, at last, but insignificant, when compared, for those features, to the vastness, the splendour, the beauty, the richness, and the gorgeousness, more or less, from day to day, displayed in the rising or the setting of the Sun; and, that for chaster beauty, and even for amount of light diffused, it is not even to be likened to the silver Moon! As a substitute, too, for either, or for both, the Aurora, in the regions of cold and night, may justly demand the admiration and the blessing of mankind; and, in regions cold and inclement, its rarity, not unaccompanied by beauty, by grandeur, and sometimes even by the terrible in appearance, may well invite the gaze and fix the attention of beholders; but, considered along with the light of the luminaries of heaven, its claims reduce themselves in quality, though certainly not in degree, to a level with those of an artificial lustre; and we almost repeat, in reference to the light of the Aurora, as compared with that of the Sun, or even of the Moon, what the poet has said in reference to the lights of our chambers:—