he did, another appeared in 1760 to have verified his calculations*.

* A comet, the most remarkable that has appeared in our hemisphere these 40 years, was first observed in London the end of September, 1807. The following are the most important particulars that we could infer from its apparent figure and motion: On the 28th of September, its declination was about 5° S. and right ascension 218°. It was conspicuous about 7 o'clock in the evening, with the brightness of a star of the second magnitude, with a short bright bushy tail, and a nucleous distinct and bright. It had passed the perihelion of its orbit, before it was any where observed in this country. It continued moving northerly at a daily rate of more than a degree, till about the end of the year. Its tail first diminishing in brightness and size, and lastly, the nucleous and comet itself. Its greatest length of tail did not exceed 14 degree; and its greatest brightness was during the month of October, while receding from the sun and the earth, or approaching towards its aphelion. On account of the oblique position of the axis of the comet's orbit, it could not be seen on its approach to its perihelion, or in its motion towards the sun. Its first appearance was near the constellation Mons-Menaulus, and it disappeared near Cygnus, or the Swan. Its figure is tolerably well represented in plate 4, fig. 6. Dr. Herschel estimated the expanse over space

of the tail, to be about nine million of miles.

It was most clearly magnified and defined by the power of the common large aperture two-feet night telescope, with three glasses, of a power about eight times. Such phenomenon as this, with feeble light or lustre, require small powers and large apertures in a refracting telescope, which is the most suitable instrument. For more ample accounts, as published by Dr. Herschel, and other skilful astronomers, see "The Philosophical Transactions, for 1808;" and "The Philosophical Magazine," Vols. 29 and 30

EDIT.

OF THE TELESCOPIC APPEARANCE OF THE PLANETS.

Though by the telescope we have been led onward in our advances towards a more powerful know ledge of the heavenly bodies, and astronomy being raised from little more than a catalogue of stars into a science; yet by this instrument men have been led into errors, and astronomers have indulged in speculations that equally deviate from sound reason, and the plain dictates of common sense.

The generality of mankind, in all ages, have considered the sun as a mass of pure elementary fire, subsisting from the creation, and supported by some unknown cause, without any occasion for the gross fuel necessary for supporting our terrestrial fires. The conjectures of astronomers have neither been so simple nor so rational; limited in their conceptions, they have not been able to perceive how fire of any kind could subsist without fuel, and have therefore supposed the sun and the earth to be of a similar substance; and, consequently, that the earth itself would be a sun if set on fire. Sir Isaac Newton has even proposed it as a query, whether the sun and fixed stars are not great earths made vehemently hot, whose parts are kept from fuming away by the vast weight and density of their superincumbent atmosphere, and whose heat is preserved by the prodigious action and re-action of their parts? Others have imagined the sun to be a body of quite a different

nature, and have even denied him to be possessed of any inherent heat, though they allow him the power of producing it in other bodies. Some have supposed, that the main body of the sun has neither light nor heat, but that it consists of a vast dark globe, surrounded on all sides with a thin covering of aerial or foggy matter, immensely splendid, which gives him the power he possesses, &c.

The only foundation for these wild conjectures, is the appearance of the sun through telescopes. By viewing it through these instruments, his face is found to be equally bright in all its parts. A slightly spotted appearance, chiefly on or near the edges, is commonly taken notice of; and, very frequently, dark spots, of various shapes and sizes, are perceived, traversing the disc from one edge to the other, These spots appear at uncertain intervals, and often change their form, while they are passing over the solar disc, or are broken in pieces, enlarge and diminish, by causes of which we are ignorant.

Those who adhere to the conjectures of Sir Isaac Newton, suppose the spots to be the smoke of new and immense volcanoes, breaking out in the body of the sun himself; while those who are pleased with the suppositions of professor Wilson, imagine them to be the dark globe, rendered visible by the displacement of the shining and surrounding matter.

Though it would be deviating from our plan to spend our time in speculations on subjects removed so far beyond the reach of human investigation : yet we can scarce refrain from observing, that there is

no foundation for supposing that the sun has any solid body. Meteors, resembling that glorious luminary in splendor, have been known to arise in the higher parts of our atmosphere, though their continuance there has been but for a short time. No one supposes that they have any solid body. It is not, therefore, unreasonable, to suppose the sun to be a vast collection of elementary fire and light, which, being sent out from him, by means unknown to us, and having accomplished the purposes for which they are designed, perpetually return to him, are sent out again, and so on. Thus, the sun continues to burn, unsupported by any terrestrial fuel, and without the least tendency to diminution or possibility of decay.

Of the Moon. From the appearance of this luminary, through a telescope, it seems probable, that there are great inequalities on her surface. Viewing her at any time, except when full, we see one of the sides notched and toothed, like a saw. Many small points, appear like stars at a small distance from the main luminous body, which join it in a little time. These are considered as the tops of high mountains, which catch the light of the sun sooner than the other parts which are lower. That these very shining parts are higher than the rest of the surface, is evident from the appearance of their shadows, which lengthen and shorten according to their situation with respect to the sun. Some astronomers have, undoubtedly, made the mountains of the moon extravagantly high; they have been much reduced

by modern calculators: Dr. Herschel has thought he discovered volcanoes on her disc. And it is supposed she has an atmosphere, because the limb of the sun has been observed to tremble just before the beginning of a solar eclipse, and because the planets become oval at the beginning of an occultation behind the moon.

Mercury being always near the sun, nothing more is distinguished by the telescope, than a variation of his figure, which is sometimes that of a half-moon, sometimes a little more, or less than half.

Venus, when in the form of a crescent, and at her brightest times, affords a very pleasing telescopic view; her surface being diversified with spots, like the moon. The diurnal motion of this planet, both as to its period and direction, has not hitherto been decidedly ascertained. Dr. Herschel concludes from his observations, that its atmosphere is very considerable. He has not been able to find the least trace of mountains, and ridicules those observers who have seen such as exceed four, five, or even six times the height of Chimboraco, the highest of our

mountains.

Mars always appears round, except at the quadratures, when its disc is like that of the moon about three days after the full. Its atmosphere is, from the ruddiness of the planet, supposed to be very dense; spots are discovered on his surface, but they do not appear fixed. Dr. Herschel has observed two white luminous circles, surrounding the poles of this pla