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.

We are familiar with the names of some writers who have contributed scarcely anything of real value to the literature of their country; whilst we are ignorant of the worth of many others who occupy a distinguished position in the commonwealth of science. Thus few persons have heard of Jeremiah Horrox, although his merits as an astronomer have been acknowledged by the most eminent scientific men who have succeeded him. But he lived in obscurity, and died young. He was not permitted by an all wise Providence to carry on his investigations for more than a few short years. He did not even enjoy the satisfaction of publishing his own discoveries. He was cut off in the midst of usefulness, and others have entered into his labors. Hence he is comparatively unknown. Happily his performances, as a skilful pioneer for the advancement of knowledge, are well authenticated, and are of sufficient importance to make his name illustrious. He paved the way for some of the most brilliant triumphs of the human intellect. Learned men have freely acknowledged this; and, in tender regard for the memory of one who expired whilst full of hope and promise, have constituted themselves the trustees of his reputation, and set their seal to his ability and worth.

The object of the following treatise is to furnish the possessors of ordinary telescopes with plain directions for their use, and a list of objects for their advantageous employment.

None but an eye-witness of the wonder and glory of the heavens can thoroughly understand how much they lose by description, or how inadequate an idea of them can be gathered in the usual mode, from books and lectures. It is but the narrative of the traveller instead of the direct impression of the scene. To do justice to this noble science,—to appreciate as we ought the magnificent testimony which it bears to the eternal Power and Godhead of Him “who by His excellent wisdom made the heavens,” we must study it, as much as may be, not with the eyes of others, but with our own.

This, however, is no easy matter: nor is the want of a telescope the only difficulty. Instruments quite sufficient for the student's purpose are far less expensive than formerly; a trifling outlay will often procure them, of excellent quality, at second-hand; and many are only waiting to be called into action. But a serious obstacle remains to the inexperienced possessor. How is he to use his telescope in a really improving way? What is he to look for? And how is he to look for it? For want of an answer, many a good instrument is employed in a desultory and uninstructive manner, or consigned to dust and inactivity.

Since the error which I discovered in the Rudolphian tables is so great, it may not be amiss to shew how the calculation may be amended in order to agree with this and other observations. I quite agree in the form of Kepler's hypotheses, and gladly receive both his annual and diurnal motion of the earth. I am of opinion also that these motions do not arise from complicated fictions of useless circles, but from natural and magnetic causes, and that they are owing to the rotation of the Sun on its axis. He knows but little of astronomy who is ignorant that the figure of the orbit is elliptical; that its centre is the body of the Sun, and not a fictitious point near it: that the motion of the planet is really unequal; that the whole apparent inequality does not proceed from its eccentricity alone; and finally, that the inclination of all the orbits to the ecliptic is not influenced by the annual motion, but is fixed and constant. No one, we repeat, who denies such facts is sufficiently acquainted with astronomical observations.

If the Solar System had comprised in itself the whole material creation, it would alone have abundantly sufficed to declare the glory of God, and in our brief review of its greatness and its wonder we have seen enough to awaken the most impressive thoughts of His power and wisdom. But that system is but as a single drop in the ocean. What boundary may be set to creation we know not, but we can trace it far enough to perceive that, as far as our senses are concerned, it cannot be distinguished from absolute infinity: and in leaving our Sun and his attendants in the background, we are only approaching more amazing regions, and fresh scenes will open upon us of inexpressible and awful grandeur. We are now to contemplate not one Sun, but thousands and myriads: — not a planetary system of subordinate globes, but aggregations of Suns; — pairs, groups, galaxies of Suns — “the host of heaven,” — all independent in unborrowed splendour, yet many evidently, and all by clear implication, bound together by the same universal law which keeps the pebble in its place upon the surface of the earth, and guides the falling drop of the shower, or the mist of the cataract.

Congratulate us, Gassendi, on clearing from suspicion your observation of Mercury, and let astronomers cease to wonder at the surprising smallness of the least of the planets, now they find that the one which seemed the largest and brightest scarcely exceeds it. Mercury may well bear his loss since Venus sustains a greater.

I observed the diameter of Venus (Chap. I.) to be 1′ 12″, the Sun being 30′; therefore the latter being 31′ 30″, the true diameter of the former is 1′ 16″. My friend Mr. Crabtree's observation agrees with this calculation: I am sure she did not appear greater; if there is any error, it is in an excess. There is no reason why any one should doubt the truth of the observation; unless indeed he is unacquainted with the telescope, or influenced by the knavery of the Peripatetics, or suspects our honesty; and I all not stay to argue either with those who have not seen this instrument or who mistrust its fidelity, for it is vain to contend with ignorance and self-will. Permit me to remind any who may suspect our good faith, how easy it would be to investigate the subject for themselves, and how little it would serve our purpose to distort truth by falsehood.

Let us then examine the opinions of others, in order that it may appear with what degree of accuracy astronomers have hitherto estimated the magnitudes of the stars.

I shall here say something which may tend to throw light upon the dimensions of the stars, and upon the horizontal parallax of the Sun, a matter of the greatest importance, and one which has been the subject of much fruitless speculation; but I will not speak dogmatically, nor, as I may say, “ex cathedrâ,” but rather for the sake of promoting discussion, and with the view of examining other men's opinions.

John Kepler, the prince of astronomers, speaking of the relative proportion of the planets (Astr. Cop. page 484), thinks it “quite agreeable to nature that the order of their magnitudes and of their spheres should be the same; that is to say, that of the six primary planets, Mercury should be the least, and Saturn the largest, inasmuch as the former moves in the smallest, and the latter in the largest orbit.”

“But as the dimensions of their bodies may be regarded as threefold, either according to their diameters, their superficies, or their bulk,” he is doubtful which should be preferred. He thinks the first proportion “to be beyond question contrary to original reasons, as well as to the observations made on the diameters by means of the Belgian telescope.” He advocates the second, because the original reasons are preferable; whilst Remus Quietanus, a man well versed in practical observations, defends the third; and with him Kepler at length agrees, retaining this proportion in the Rudolphian tables.