Fienus, in his curious little book de viribus imaginationis, records from Donatus the case of a man, who fancied his body increased to such a size, that he durst not attempt to pass through the door of his chamber. The physician, believing that nothing could more effectually cure this error of imagination, than to shew that the thing could actually be done, caused the patient to be thrust forcibly through it: who, struck with horror, and falling suddenly into agonies, complained of being crushed to pieces, and expired soon after *.-Reason, certainly, was not concerned here. The other case, as related by Van Swieten in his Commentaries upon Boerhaavet, is that of a learned man, who had studied, till he fancied his legs to be of Glass; in consequence of which, he durst not attempt to stir, but was constantly under anxiety about them. His maid bringing one day some wood to the fire, threw it carelessly down; and was severely reprimanded by her master, who was terrified not a little for his legs of glass. The surly wench, out of all patience with his megrims, as she called them, gave him a blow with a log upon the parts affected which so enraged him, that he instantly rose up, and from that moment recovered the use of his legs.Was reason concerned any more here? or, was it not ra ther one blind impulse acting against another? : The comet which now appears above our western_horizon in the evening, though in apparent size not larger than a star of the second magnitude, will probably continue visible some weeks, and engage the attention of all P. 131. L. Bat. 1635, the astronomers in Europe; and should it approach nearer the earth, may excite the surprize and alarm the fears of the multitude. Comets, according to the observations of the most celebrated astronomers, are solid opaque bodies of different magnitudes, and are principally distinguished from the planets by their outline being more irregular, and by a long track of a luminous matter, called their tail, which sometimes stretches a great way across the heavens, and always issues from the body upon the side farthest from the sun. The number of comets belonging to our system is not yet accurately ascertained, but it is supposed that there are about 450-the orbits of 59 of which have been already calculated, and the period of their revolution ascertained. Like the planets, they also move round the sun, but in very long ellipses, approaching very near it in one situation, called their perihelion, and receding to an immense distance in another-the extremity of which is termed their aphelion. The orbits of the comets are in general inclined to the plane of the ecliptic, in large an gles, and consequently they are not likely to give any disturbance to the earth, though formerly their appearance gave birth to very serious apprehensions. It was the very accurate observations made by Sir Isaac Newton, on the great comet of 1680, which first proved them to be a kind of planets moving in very eccentric elliptical orbits, and with accelerated velocity as they approach their perihelion. That remarkable comet was supposed to be the same which had appeared in 1106, in the time of Henry I. In the year 531, in the Consulship of Lampadius; and in the year 44 B. C. before Julius Cæ sar was murdered. Its next appearance will be in the year 2255. The comet which appeared in 1759 was pretty accurately predicted by the learned Dr. Halley, and may again be expected to appear about the year 1835. The illustrious Newton calculated, that the heat of the great comet of 1680, in its near approach to the sun, must have been 2000 times greater than that of red hot iron; consequently, if we suppose that comet to be of the same dimensions with the earth, and to cool no faster than red hot iron, it would require upwards of a hundred millions of years to cool; and from its periodical revolution in the short space of 575 years, must remain for ever in a state of the most violent ignition. This comet, according to Halley, "in passing through its southern node, came within the length of the sun's semidiameter of the earth's orbit." Had the earth been then in that part of her orbit nearest to that node, the mutual gravitation of two such large bodies, with so rapid a motion as that of this comet, must not only have deranged the plane of the earth's orbit, but by coming in contact with the earth (there are comets which are supposed never to come within the bounds of our solar system) the shock must have reduced this beautiful frame to its original chaos, or transported it beyond the limits of the Georgium Sidus, into the boundless depth of infinite space. Comets may serve as conductors of that subtle and active fluid from the sun to the most remote regions of the planetary system; or if, as some have maintained, light be a modification of the electric fire, they may attract and convey back the light emitted from the solar atmosphere, and prevent the decrease which must ensue from the prodigious velocity with which the particles of light are constantly streaming forth from every part of the sun's surface. The celebrated La Lande says, the number of comets which have been observed since the invention of telescopes is so great, that it may be doubted whether they should be reckoned by hundreds or by thousands. Their use in the system of nature, though unknown to us, must, doubtless, be of the first importance. The largest comet recorded in history, is said, by Seneća, to have appeared not less than the sun :- -" paulo ante Acharium bellum cometes effulsit non mina sole." o. 2 lib. 7, c. 15. The comet lately discovered, has been very distinctly observed in Scotland, and particularly on the evening of Monday the 12th inst. when the following phenomena were distinctly seen from Stob's Castle, Roxburghshire.. It became visible immediately after twilight; at a considerable elevation in the heavens, nearly due west, and set about one-half past eight o'clock, within a few degrees of north west. The nucleus, or star, when viewed through a small telescope, appeared about the size of a star of the first magnitude, but less vivid, and of a pale dusky colour. The atmosphere of the comet, owing to the limited power of the telescope, was barely perceptible. The tail, daily increasing in magnitude and splendour, as the comet approaches the sun, appeared sometimes extremely brilliant, seeming to be a vibration of luminous particles, somewhat resembling the Aurora Borealis, and at other times almost to disappear. From the arch described by the comet in the heavens, in the short space of two hours, its velocity must be immense. By the nearest computation which circumstances and situation allowed, supposing the comet to be as far distant as the Sun, or about 12,000 diameters of the earth, it must be moving in the present stage of its perihelion, at the amazing velocity of nearly a million of miles an hour, or upwards of 16,000 miles a minute! Such astonishing rapidity is indeed almost inconceivable; but the velocity of the comet observed at Palermo, in 1770, by Mr. Brydone, was still more remarkable, which, in 24 hours, described an arch in the heavens of upwards of 50 degrees in length, and was computed by that ingenious gentleman to be moving at the rate of 6) millions of miles in a day, or upwards of 40,000 miles in a minute! Had With a telescope, admitting a large quantity of light, the nucleus was distinctly perceived near London; the luminous matter which formed the tail surrounded the whole body of the comet; the outline of the tail was well defined at some distance from the point of divergence. Near the northern side a small telescope star was seen about fifteen seconds apparent distance from the tail. Two small stars were also near the head of the comet. the comet remained longer above the horizon, the direction of its path might have been readily marked by these stars. The tail resembles the electric aura, or a bright ray of the Aurora Borealis. It is highly probable that it is not formed by heated vapour, as some have supposed, but by an immense stream of electric fluid, emanating from the body of the comet, in a direction opposite to the sun. The brilliancy of the stars is not diminished, nor does their light suffer any refraction when seen through the tail of a comet. OBSERVATIONS UPON ANTS. IN A SERIES OF LETTERS TO A FRIEND, "Go to the Ant, thou sluggard, and be wise." You have been pleased to write to me, that you desire to know more particularly what observations I have made upon some of the smallest insects that are in nature. I wish I could fully satisfy your curiosity, by giving you an exact, and, as it were, an anatomical description of those little animals. I should be glad to inform you how ants are generated, to treat of their different species, to shew you in what order they are placed in their nests, and to mention many other curious particulars, which perhaps I shall be able to communicate to you hereafter. I had neither a sufficient time, nor proper microscopes, to take an exact view of all those things; and therefore I hope you will be contented with such observations as I can now impart to you. I made those observations in the country, where I spent all the summer without company, in a place which appeared to me very melancholy. One would think, that God was pleased to raise ants, to bring me off from idleness, and make me hear the voice of the wise man, who says, Vade ad formicam, O piger. And indeed those insects are not unworthy of our attention, since the Scripture commends them; and such a curiosity may contribute to our improvement. A particular view of the smallest works of nature, affords new reasons to admire the wisdom of God: and, generally speaking, the conduct of those small insects appears more orderly, and even more edifying, than that of men. In a room next to mine, which had been empty for a long time, there was upon a window a box full of earth, two foot deep, and fit to keep flowers in. That kind of parterre had been long uncultivated; and therefore it was covered with old plaster, and a great deal of rubbish that fell from the top of the house, and from the walls, which, together with the earth formerly imbibed with water, made a kind of dry and barren soil. That place lying to the south, and out of the reach of the wind and rain, besides the neighbourhood of a granary, was a most delightful spot of ground for ants; and therefore they had made three nests there, without doubt for the same reason that men build cities in fruitful and convenient places, near springs and rivers. Having a mind to cultivate some flowers, I took a view of that place, and removed a tulip out of the garden into the box; but casting my eyes upon the ants, continually taken up with a thousand cares, very inconsiderable with respect to us, but of the greatest importance for them, they appeared to me more worthy of my |