A new comet having been discovered, the first thing an astronomer does, is to obtain 3 observations of it, whereby he may compute the elements of the orbit. He then examines a catalogue of comets, to see if he can identify the newly-found stranger with any that have been before observed. The value of a complete catalogue is therefore obvious, and as nothing of the kind has, as far as we are aware, been published for some years, we have been led to compile a new one.

In the preparation of the following, care has been taken that only the most reliable orbits that were to be obtained should be inserted, the general rule being to prefer the one which was derived from the longest arc, other things being satisfactory. Among the authorities consulted may be mentioned Pingré, Hussey, Olbers, Cooper, Hind, Arago, and others.

Owing to its proximity to the Sun, observations of the physical appearance of this planet are obtained with difficulty, and even then are liable to much uncertainty. Schröter, who paid considerable attention to Mercury, thought he had detected traces of the existence of high mountains on its surface; his observations, however, were not confirmed by Sir W. Herschel. Mercury exhibits phases similar to those of the Moon. At its maximum elongations, only half its disc is illuminated, but as it approaches its superior conjunction, the breadth of the illuminated part increases, and its form becomes gibbous, and ultimately circular in conjunction, when, however, the planet is lost in the Sun's rays and invisible; on emerging, the gibbous form is still preserved, but the gibbosity is on the opposite side. The breadth of the illuminated part diminishes as the planet draws near its greatest elongation, when it again appears like a half moon, and continues to become more and more crescented as it approaches the inferior conjunction; having passed this, the crescent (now on the opposite side) gradually increases until the planet again reaches its greatest elongation.

It is not our intention, in the present Book, to enter into a regular history of astronomy: that would occupy more space than we could afford, more especially as there are several works, now extant in the English language, on the subject; all therefore we shall do, will be to lay before the reader a chronological summary of the rise and progress of the science from the earliest period.

The following list has been compiled with some care; but variable star information is often of questionable authenticity, the accounts of different observers being quite as variable as the stars themselves, or even more so. This list will, it is ioped, be found to be the most complete ever published, special pains having been taken to make it so: as amateurs, having time and instruments at their command, may render good service by looking after these objects. The letter D appended to the name of a star signifies that its position is given for some other epoch than 1860: the symbol < signifies that the star's minimum magnitude fell below that given; but how much, is unknown.

To account for the nature and origin of aerolites, the following hypotheses have been propounded: —

First.—It is supposed that the matter composing them has been drawn up from the surface of the Earth in a state of infinitely minute subdivisions, as vapour is drawn from liquids; that, being collected in clouds in the higher regions of the atmosphere, it is there agglomerated and consolidated in masses, and falls by its gravity to the surface of the Earth; being occasionally drawn from the vertical direction which would be imparted to it by gravity by the effect of atmospheric currents, and thus occasionally striking the Earth obliquely. We shall call this the atmospheric hypothesis.

Secondly.—It is supposed that meteoric stones are ejected from volcanoes, with sufficient force to carry them to great elevations in the atmosphere, in falling from which they acquire the velocity and force with which they strike the Earth. The oblique direction with which they strike the ground is explained by the supposition that they may be projected from the volcanoes at corresponding obliquities, and that, by the principles of projectiles, they must strike the Earth at nearly the same inclination as that with which they have been ejected. This we shall call the volcanic hypothesis.

The comets which might be included under the above head are so numerous as to make it impossible for all to receive proper attention; we must therefore limit ourselves to some of the most interesting, commencing with—

The Comet of 1858 (vi). On June 2 in that year Dr. G. B. Donati, at Florence, descried a faint nebulosity slowly advancing towards the north, and near the star λ Leonis. Owing to its immense distance from the Earth (240,000,000 miles), great difficulty was experienced in laying down its orbit. By the middle of August, however, its future course, and great increase of brightness in September and October, had been ascertained with entire certainty. Up to this time (middle of August) it had remained a faint object, not discernible by the unaided eye. It was distinguished from ordinary telescopic comets only by the extreme slowness of its motion (in singular contrast to its subsequent career), and by the vivid light of its nucleus: “ the latter peculiarity was of itself prophetic of a splendid destiny.” Traces of a tail were noticed on August zo, and on August 29 it was faintly perceptible to the naked eye; for a few weeks it occupied a northern position in the heavens, and was thus seen both in the morning and evening sky.

English literature, abundant though it be in other respects, is undoubtedly very deficient in works on Astronomy. Our choice is limited either to purely elementary books, few in number, on the one hand; or to advanced treatises, of which there is a similar paucity, on the other. The present work is designed to occupy a middle position between these two classes; to be attractive to the general reader, useful to the amateur, and “ handy” also, as an occasional book of reference, to the professional astronomer.

In pursuance of the plan laid down from the first, theoretical matter is, as a rule, excluded; but in many cases, it has been thought desirable not to abide with perfect strictness to the limitation. All speculations however, bearing on the origin of the created universe have been carefully avoided, sufficient mischief having already been done by the artful sophistries of those who delight in what they are pleased to term “ Free Philosophical Enquiry.”

The most recent discoveries in all branches of the science, will be found incorporated with information of older date. The Chapters on Comets may be instanced as an example; and the catalogues belonging to them, will, it is anticipated, be found serviceable to the professional computer.

The following Catalogue, it is almost needless to say, is founded upon that most valuable one of Pingré's, but this is the first time that a catalogue of the kind has been printed in such a full tabular form,—a great convenience for purposes of reference.

Our Catalogue ia comprised in 29 octavo pages, whereas Pingré's extends to no less than 300 quarto pages: to his work, therefore, the reader who desires to know more of any of the following comets is referred; its value is greatly enhanced by the copious references to his authorities which he gives: would that English authors, generally, would take a hint in that respect! Pingré's Cométographie was compiled almost a century ago; since his time, however, numerous and important accessions have been made to our stock of knowledge, more especially by E. Biot, who has translated several Chinese chronicles and catalogues of stars and comets, not previously properly understood, in some cases not understood at all. Hind's valuable Catalogues in the Companion to the Almanac, for 1859 and 1860, have also been consulted.

It is wholly impossible to give a list of the authorities; the last column in the Catalogue will afford an idea of the number. Pingré gives references to all the works in which mention is made of any fact; we, of course, have only been able to give one or two of the chief.

But I leave these patrons of circles and equality, these artificers of an useless labyrinth, and their hypotheses which are faulty in their construction and incapable of amendment. For although the measures of the eccentricities of the orbits, together with the mean motions, might be corrected so as to resemble this and other observations; yet as the stars are governed by different laws from those which they have invented, it is impossible by a complication of such circles to bring about an entire agreement with appearances.

I hasten therefore to that prince of astronomers, Kepler, to whose discoveries alone, all who understand the science will allow that we owe more than to those of any other person. I venerate with the greatest honour and admiration his sublime and enviably happy genius; and if necessary, I would defend with my best efforts the Uranian citadel of the noble hero who has so much surpassed his fellows, nor shall any one while I live, violate his ashes with impunity. His death was an event that must ever have happened too soon; the science of astronomy received the lamentable intelligence whilst left in the hands of a few trifling professors who had kept themselves concealed like owls until the brightness of his sun had set.

Whilst I was meditating in what manner I should commence my observation of the planet Venus so as effectually to realize my expectations, the recent and admirable invention of the telescope afforded me the greatest delight, on account of its singular excellence and superior accuracy above all other instruments. For although the method which Kepler recommends in his treatise on Optics, of observing the diameter and eclipses of the sun through a plain aperture without the aid of glasses, is very ingenious, and in his opinion, on account of its freedom from refraction, preferable to the telescope; yet I was unable to make use of it, even if I had wished to do so, inasmuch as it does not shew the sun's image exactly, nor with sufficient distinctness, unless the distance from the aperture be very great, which the smallness of my apartment would not allow. Moreover I was afraid to risk the chance of losing the observation; a misfortune which happened to Schickard, and Mögling, the astronomer to the Prince of Hesse, as Gassendi tells us in his Mercury: for they, expecting to find the diameter of Mercury greater than it was reasonable to anticipate, made use of so large an aperture that it was impossible to distinguish the planet at all, as Schickard himself has clearly proved; and even though Venus gave promise of a larger diameter, and thereby in some measure lessened this apprehension, and I was able to adapt the aperture to my own convenience, yet in an observation that could never be repeated, I preferred encountering groundless fears to the certainty of disappointment.