whose number appears so far to surpass that of the primary and secondary planets of our system. It was long ago predicted by Seneca, a Roman philosopher who lived in the first century of the Christian era, "that the time will come when the nature of comets and their magnitude will be demonstrated, and the courses they take so different from those of the planets; and that posterity will wonder that the preceding ages should be ignorant in matters so plain and easy to be known." In order that this prediction may be fully realized, it is requisite that we should become acquainted with all the observations that have hitherto been made, and the facts in relation to these bodies which have been ascertained; that we should compare the various observations with each other, and attend to the minutest circumstances and phenomena connected with comets; that numerous observers should be appointed to survey different portions of the firmament, both in the northern and southern hemispheres, that no comet that comes within the limits of our vision may pass unobserved; and that when a comet of a large size approaches near the centre of our system, every minute particular in reference to its motions, and the changes which take place in its nucleus, envelope, and tail, be carefully observed and delineated by accurate representations.

Whatever opinions we may adopt as to the physical constitution of comets, we must admit that they serve some grand and important purpose in the economy of the universe; for we cannot suppose that the Almighty has created such an immense number of bodies, and set them in rapid motion according to established laws, without an end worthy of his perfections, and, on the whole, beneficial to the inhabitants of the system through which they move.

They display the wisdom of their Creator in the arrangements of their orbits and motions. As we have every reason to conclude that at least thousands of those bodies traverse the solar system in all directions, and are certain that their orbits are inclined in every possible degree to one another and to the orbit of the earth, so we find that they have been so admirably arranged by Divine Intelligence that no one of them interferes with another, or with the courses of the planets, so as to produce concussion or disorder. The orbits of some comets, indeed, are found to approach very near, and even to cross the orbit of the earth and the orbits of several

of the other planets, and, consequently, there is a possibility that a comet might come into concussion with our globe; and this consideration shows us that we are dependant for our present security and comforts on the wise arrangements of the Almighty, in securing perfect harmony and order amid apparent danger and confusion. But we have no evidence that such a catastrophe has ever happened, either in the case of the earth or of any of the other planets, or that one comet has ever impinged upon another. Believing that every object and event in the universe is arranged and directed by an Omnipotent Contriver, we must admit that when the Almighty formed the wondrous plan of creation, "foreseing the end from the beginning," he arranged the periods and the velocities of comets in such a manner that, although occasionally crossing the planetary orbits, they should not pass these orbits at the time when the planets were in their immediate vicinity. And should such an event ever occur, we may rest assured that it is in perfect accordance with the plan and the will of Omnipotence, and that it is, on the whole, subservient to the happiness and order of the intelligent universe, and the ends intended by the Divine government. If there are thousands, and perhaps millions of comets of all descriptions traversing every part of the planetary regions, in orbits of every degree of inclination, of extent, and of eccentricity, we are sure that none but a Being of infinite power and intelligence could have arranged such a vast and complicated system, so as to have prevented numerous interferences and disasters, and to make the whole move onward for ages in perfect harmony.

The system of comets likewise presents to us a display of the omnipotence and grandeur of the Deity. The number of these celestial visiters, the vast magnitude of their tails, envelopes, and nuclei, and the amazing velocity with which they wheel their courses through the ethereal regions, exhibit before us objects of astonishing grandeur, and evince the almighty power of Him who at first impelled them in their rapid career. The diameter of the nucleus of the comet of 1807 was estimated by Schroeter at 4600 miles, and that of its coma 120,000 miles. Besides its principal tail, it shot forth coruscations to the extent of four millions, six hundred thousand miles. The nucleus of the comet of 1811 was, according to the same observer, 50,000 miles in diameter, its coma or envelope 947,000 miles, and its tail or train of light sixty millions of miles in length,

or more than half the distance between the earth and the sun. Let us conceive such a body, like the comet of 1680, traversing the immense spaces of creation with a velocity of ten hundred thousand miles an hour, and drawing after it a luminous train a hundred millions of miles in length, approaching at one time so near the sun that his circumference would appear to fill the greater part of the firmament, and then rushing back through the depths of immeasurable space thousands of millions of miles beyond the orbit of Uranus, and displaying its majestic train to the other planetary worlds of our system, and we have presented to our mental eye an object of peculiar grandeur and magnificence, different from everything else which the planetary system exhibits, and which displays in an eminent degree Were the power and magnificence of the Great Creator. such a body to sweep along the regions which lie in the immediate vicinity of our globe, at the distance of ten or twelve thousand miles, nothing that we have ever beheld or can well conceive could be compared to the majestic grandeur of the scene, which would overpower the mind with astonishment and with terror. On the view of such an object, sweeping along with such velocity, we could scarcely refrain from exclaiming, in the language of inspiration, "Great and marvellous are thy works, Lord God Almighty!" What, then, shall we think of thousands of such mysterious orbs winging their flight in every direction, in perfect regularity and order, through the immensity of space! Surely these are the wonderful works of Him who is mighty in operation and perfect in knowledge.

In all the works of the Deity, we must likewise admit that his goodness is displayed, although we may not be able to trace the mode of its communication; for we may lay it down as an axiom, that wherever wisdom and omnipotence are exhibited throughout the Divine economy, there is also a display of beneficence, which appears to be one prominent design of all the works of God. Comets have long been considered as objects of terror and as omens of impending calamities; but there can be no question that they are as intimately connected with a system of benevolence as are the solar radiations and their benign influence on our globe and on the other planets. It has been conjectured that comets may supply moisture to the other planets, and invigorate the vital principle of our atmosphere; that they may recruit the sun with fresh fuel, and

repair the consumption of his light; or that they may be the agents for dispersing the electric fluid through the planetary regions; and although there is little probability that such conjectures are accordant with fact, yet it may be admitted that comets may produce a physical influence of a beneficial nature throughout the solar system. But what I conceive to be one of the main designs of the Creator in the formation of such a vast number of splendid bodies is, that they may serve as habitations for myriads of intellectual beings, to whom the Almighty displays his perfections in a peculiar manner, and on whom he bestows the riches of his beneficence. Whatever may be the intention of those comets which are destitute of a nucleus, this, in all probability, is the chief design of those which are large and which are invested with a solid nucleus; and the same arguments which we formerly brought forward to prove that the planets are inhabited, might be adduced in proof of the inhabitability of comets. If this position be admitted, then we ought to contemplate the approach of a comet, not as an object of terror or a harbinger of evil, but as a splendid world, of a different construction from ours, conveying millions of happy beings to survey a new region of the Divine empire, to contemplate new scenes of creating power, and to celebrate in loftier strains the wonders of Omnipotence. Viewing the comets in this light, what an immense population must be contained within the limits of the solar system, which gives room for the excursions of such a vast number of these bodies! and what an incalculable number of beings of all ranks must people the wide-extended universe!*

* The most complete account of the phenomena, &c., of comets I have seen, is a treatise on this subject in manuscript, by the Rev. Thomas W. Webb, of Tretire, near Ross. This treatise contains, I. A copious introduction, imbodying a variety of interesting general remarks in relation to this subject. 2. A particular account of the comet of 1807, according to the observations of Sir William Herschel. 3. A description of the same comet from the observations of Dr. Johan. Hieron. Schroeter. 4. An account of the great comet of 1811, according to the observations of Sir W. Herschel. 5. A particular description of the phenomena of the same comet, according to the observations of Schroeter. 6. A description of the second comet of 1811, according to the observations of Sir W. Herschel. These observations, particularly those of Schroeter, contain the most minute descriptions which have hitherto been given of the phenomena of this class of the celestial bodies, and will be found of essential service, not only to amateur observers, but to astronomers of every description. They have been extracted and arranged chiefly from the "Philosophical Transactions," and the works of Schroeter,

which were published in the German language. The Appendix, or Second Part, which occupies nearly half the volume, comprises a lucid investigation of the following topics: 1. Comparison of observations. 2. Examination of hypotheses. 3. Nature, light, and solidity of comets. 4. Colours of comets. 5. Brightness of comets. 6. Divided tails of comets. 7. Coruscations of comets. 8. Miscellaneous notices concerning remarkable comets. 9. On the influence of comets. 10. Losses to science, containing an account of the disasters which befell Schroeter, Hevelius, &c. 11. Hints to amateur observers. This volume contains 230 4to pages, besides a great number of copious notes, and forty-six figures of the different appearances of comets. It indicates a very great degree of labour and research, which the astronomer alone will be fully able to appreciate. The author appears to have consulted most of the works which have been published on the subject in the English, Latin, French, and German languages, besides imbodying a number of original observations and remarks. And, what is not among the least important features of the work, the author takes every opportunity of introducing such moral reflections as the subject naturally suggests, and of directing the contemplations of his readers to Him who sits on the throne of the universe. The observations of Schroeter contained in the preceding pages have been extracted from this volume. It is to be hoped that the worthy author, who is already known to a considerable portion of the scientific world by his communications to periodicals and scientific associations, will soon receive encouragement to lay this work before the public.