THE SPECTRE OF THE BROCKEN. WHEN the connexion of events with each other is unknown, ignorance refers them to what is called "Chance;" and superstition, which is ignorance in another form, to the agency of some superior malevolent or benevolent being: but philosophy endeavours to discover the foregoing link in the chain of events.

Near to the Hartz mountains in Germany, a gigantic figure has, from time immemorial, occasionally appeared in the heavens. It is indistinct, but always resembles the form of a human being. Its appearance has ever been considered a certain indication of approaching misfortune. It is called the Spectre of the Brocken (the name of the hill). It has been seen by many travellers. In speaking of it, M. Jordan says, "In the course of my repeated tours through the Hartz mountains, I often, but in vain, ascended the Brocken, that I might see the spectre. At length, on a serene morning, as the sun was just appearing above the horizon, it stood before me, at a great distance, towards the opposite mountain. It seemed to be the gigantic figure of a man. It vanished in a moment." In September 1796, the celebrated Abbé Hay visited this country. He says, "After having ascended the mountain for thirty times, I at last saw the spectre. It was just at sunrise, in the middle of the month of May, about four o'clock in the morning. I saw distinctly a human figure of a monstrous size. The atmosphere was quite serene towards the east. In the south-west a high wind carried before it some light vapours which were scarcely condensed into clouds, and hung round the mountains upon which the figure stood. 1 bowed: the colossal figure repeated it. I paid my respects a second time, which was returned

with the same civility. . I then called the landlord of the inn, and having taken the same position which I had occupied before, we looked towards the mountain, when we clearly saw two such colossal figures, which, after having repeated our compliment, by bending their bodies, vanished."

Now for an explanation of this appearance. "When the rising sun throws his rays over the Brocken upon the body of a man standing opposite to fleecy clouds, let the beholder fix his eye steadily upon them, and in all probability he will see his own shadow extending the length of five or six hundred feet, at the distance of about two miles from him."

RAIN.

Ir is a mortifying confession to make, that our knowledge of the cause of a phenomenon so constantly occurring as rain, is still extremely imperfect; yet such is the case, for there are many circumstances regarding the formation of rain that are not yet satisfactorily accounted for. We shall therefore content ourselves with a statement of a few facts respecting rain that are interesting, without entering into discussions concerning their causes, or, at most, briefly alluding to the more plausible solutions.

It has been observed, that more rain, on an average, falls on land, near the ocean, than on the sea itself; this may be accounted for by supposing the currents to bring the surplus of vapour, formed above the sea, over the land, before it meets with another current by which it may be condensed.

More rain falls in mountainous countries than on extensive plains. Thus, in England the annual average at Kendal is 56 inches, though that for the whole island is only 33; and a similar inequality exists for other districts, not only in Britain

but other countries.

At Geneva the average rain is 42 inches, and at Great St. Bernard 63; at Jolmezzo, in Friuli, 82; at Carfagnano, in the Apennines, 92, annually; while that for Europe generally is only 35, and for Paris only 22. There are several causes that may concur to produce this inequality. 1. The partial currents that exist in mountainous districts, caused by the unequal heating of large masses of rocky mountains, one side of which is exposed to the sun's rays, while the other is in shade. 2. The attraction that elevated mountainous ridges present to passing clouds, causing them to accumulate in such localities. 3. The existence of lakes and basins of water in the hollows of mountainous districts, which are sources of constant and abundant evaporation. The effects of lofty mountainchains, or high table-lands, in producing the most striking difference between the countries they separate, as regards the quantity and period of the rains in each, is strikingly exemplified in the Indian peninsula. The rainy months at Bombay are from June to October inclusive, while along the opposite Coromandel coast the seasons are exactly the reverse, apparently owing to the central table-land.

In South America the lofty chain of the Andes produces a similar discrepancy; in those parallels, where the chain approaches the Pacific, the boundless plains on the east, within the tropics, are deluged by the periodical rains from November to May, while the narrow strip of land to the west is almost entirely exempted from rain.

THE AURORA. THE Aurora Borealis, or Australis, as it is termed, accordingly as it is seen in the northern or southern hemispheres, is a meteor that justly excites the greatest interest, both from its intrinsic singularity and

beauty, and because it has hitherto defied all attempts to account satisfactorily for it. Aurora is mostly seen in these latitudes in Autumn, or during cold weather, and its frequency and brilliancy appear to augment, the higher the latitude.

Mr. Dalton describes the brilliant Aurora, which appeared on the 13th of October, 1792, in the following terms: "Attention was first excited by a remarkable red appearance of the clouds to the south, which afforded sufficient light to read by at eight o'clock in the evening, though there was no moon nor light in the north. From half past nine to ten there was a large luminous horizontal arch to the southward, and several faint concentric arches northward. It was particularly noticed, that all the arches seemed exactly bisected by the magnetic meridian. At half-past ten o'clock streamers appeared very low in the southeast, running to and fro from west to east; they increased in number, and began to approach the zenith apparently with an accelerated velocity, when, all of a sudden, the whole hemisphere was covered with them, and exhibited such an appearance as surpasses all description. The intensity of the light, the prodigious number and volatility of the beams, the grand intermixture of all the prismatic colours in their utmost splendour, variegating the glowing canopy with the most luxuriant and enchanting scenery, afforded an awful, but, at the same time, the most pleasing and sublime spectacle in nature. Every one gazed with astonishment, but the uncommon grandeur of the scene lasted only about one minute; the variety of colours disappeared, the beams lost their lateral motion, and were converted into the flashing

The meridian passing through the mag netic North and South, as indicated by a needle at the place; the true meridian passes through the pole and zenith, and cuts the horizon in the true North and South points.

radiations. Altogether, this Aurora lasted for several hours; there were many meteors, or falling stars, seen at the same time, but they appeared to be below, and unconnected with the Aurora."

Captain Parry, in his account of the third voyage to discover the North-West Passage, during the years 1824-5, states that the Aurora was observed twice in October, five times in November, seven in December, fifteen in January, thirteen in February, and five times in March. By far the greater part of these phenomena assumed one general character, and occupied nearly the same position. It usually consisted of an arch, sometimes tolerably continuous, but more frequently broken into detached irregular masses, or nebulæ, of light, extending from about West to South-East, (true,) which bearings correspond with N.E. by N. and W. by S. (magnetic). It sometimes however, extended a few points beyond these bearings, but very rarely occupied any of the northern part of the heavens." "On the whole, the arch seems to have been more frequently bisected by the plane of the magnectic than by that of the true meridian. The altitude of the upper margin of a permanent arch seldom exceeded ten or fifteen degrees, and from this coruscations were generally observed, shooting towards the zenith. In a few instances the arch itself passed as high as the zenith; and on a single occasion, the 28th of January, 1825, its direction was from true North to South. The lower edge of the arch was generally well defined and unbroken, and the sky beneath it appeared, by contrast, so exactly like a dark cloud, (to me often of a brownish colour,) that nothing at the time of viewing it could well convince one to the contrary, except the stars shining there with undiminished lustre.

"About midnight, on the 27th of January, this phenomenon broke out in a single compact mass of brilliant yellow light, situated about a S. E. bearing, and appearing only a short distance above the land. This mass of light, notwithstanding its general continuity, sometimes appeared to be evidently composed of numerous pencils of rays, compressed as it were, laterally into one; its limits, both to the right and left, being well defined, and nearly vertical. The light, though very bright at all times, varied almost constantly in intensity, and this had the appearance (not an uncommon one in the Aurora,) of being produced by one volume of light overlaying another, just as we see the darkness and density of smoke increased by cloud rolling over cloud. While we were admiring the extreme beauty of this phenomenon from the observatory, we all simultaneously uttered an exclamation of surprise, at seeing a bright ray of the Aurora shoot suddenly downward from the general mass of light, and between us and the land, which was then distant only three thousand yards. Had I been the sole witness of this, I should have received with caution the evidence of my own senses, but the appearance conveying precisely the same idea to three individuals at once, I have no doubt the ray of light actually passed within that distance of us.

"It was always evident enough, that the most attenuated light of the Aurora sensibly dimmed the stars, like a thin veil drawn over them. We frequently listened for any sound proceeding from this phenomenon, but never heard any."

It appears that the duration of the Aurora is very variable; sometimes it forms and disappears in the course of a few minutes, at others it lasts during the whole of the night,

and even for two or three days together. Muschenbroek observed one in 1734, which lasted ten successive days and nights.

The appearance of Aurora, in high northern latitudes especially, has been supposed to be accompanied by audible sounds, variously described by different narrators;according to some it resembles the rustling of a silk flag, when waved to and fro in the air; by others it has been compared to a crackling sound; by others again to the rushing of wind, &c. The decided evidence of Captain Parry and of Mairan against the existence of any sound accompanying the appearance of Aurora, would seem to imply that this, like the other exaggerated statements of early writers, originated in the suggestions of imagination uncontrolled by the discipline of philosophy. Motion and sound are so commonly conjoined, that it requires some effort to prevent the appearance of the one from necessarily exciting, by association, the idea of the other; and when electricity was especially assigned as the cause of Aurora, the peculiar noise attending the transmission of the fluid through nonconducting substances, was, perhaps, presumed to be also an attendant of so remarkable a manifestation of it.

The first remarkable fact attending the appearance of Aurora which might seem to lead to some explanation of its cause, is the disturbance that it occasions in the magnetic declination, dip, and intensity, as indicated by the needle. And since these perturbations have been observed, when the Aurora which accompanied them was not visible above the horizon of the place, owing to its remoteness, it seems reasonable to suppose that there must be some connexion between this atmospheric and the unknown agency which produces electrical and magnetic phenomena. Never

theless, the only plausible solution of the problem which has yet been given, does not appear more immediately connected with electric agency than every other chemical action. The hypothesis alluded to is, that Aurora is the light given out during the congelation of vapour or water suspended in the atmosphere; observation has shown that under certain circumstances light is given out during the solidification of water, as heat nccessarily always is; and since crystallization is now known to be intimately connected with electric or galvanic agency, the action of Aurora on the needle is thus obscurely hinted at. But our readers must bear in mind that our knowledge of the facts themselves attending the appearances of Aurora, are far too vague and scanty to admit of any but the purest hypothetical reasoning on the subject, and that it is still involved in complete obscurity, which nothing but longrepeated and accurate observation can remove.

THE MIRAGE.

THE first march from Abusheher we had to pass over a desert plain of considerable extent, on which I amused myself by watching narrowly the various changes, as we were near or remote from it, of that singular vapour, called by the French MIRAGE, and by the Arabs and Persians SIRAB.

The influence of this vapour in changing the figure of objects is very extraordinary; it sometimes gives to those seen through it the most fantastical shapes, and, as a general effect, it always appears to elevate, and make objects seem much taller than they really are. A man, for instance, seen through it at the distance of a mile and a half upon the level plain, appears to be almost as tall as a date-tree.