ASTRONOMICAL SCIENCE.

Every one has heard of the Wonders of Astronomy, but few entertain an adequate conception of its practical utility. It appeare to me, therefore, that to some at least, I should be rendering no unacceptable service. If I were to endeavour for a short time to divert your thoughts from the more marvellous aspects of the subject, and fix them on some of the particulars which bring it home more immediately to the thoughts and the business of mankind-had great capacities, or great attainments been essential to the accomplishment of my purpose, I should have been silent-but believing that a simple and lucid statement of facts, is all that will be required, I shall not hesitate to proceed with the discussion of the subject. In doing so, I shall have to speak of several other Arts and Sciences, in order to show that they are all indebted to the influence of Astronomy for their practical advancement. At the same time I wish it to be distinctly understood, that I have not the slightest intention of depreciating the value of any other branch of study—either in nature or in art; nor is it intended to deny that astronomy is much indebted to other arts and sciences for the comparative perfection of its present state. All the Arts or Sciences are more or less connected and dependent upon each other, and all will be valued in proportion as they are understood. But unless we are utterly to repudiate the faculty of discrimination, we cannot estimate them all at precisely the same value. Without then in the least. wishing to disparage the interest or importance of any other department of human knowledge, it will be my endeavour on this occasion, from an induction of particulars to shew that Astronomy, from the benefits which it has already conferred -and which it is destined hereafter to confer-upon the world is entitled to pre-eminent gratitude and admiration.

If we have not read the annals of the past with a purblind perversity of judgment the most cursory glance at the History of Natural Philosophy will be sufficient to shew that Astronomy has been the Originator of some-the promoter of others, and the undoubted precursor of all those great advances in modern science which so eminently distinguish the present age. Let us then for a few moments cast our thoughts backward over a period of somewhat less than two hundred years, to the time when Newton made his great discoveries, and briefly compare the present with the past, passing geology, optics. chemistry, geography, chronology, borology, metrology, mechan

ics, mathematics, navigation and mental progress, under a short and rapid review.

Geology, for instance, previous to the epoch to which I have just alluded had no existence. The theories of Burnett, Whiston, Buffon and Hutchinson were nothing better than philosophic dreams, mere reveries of the imaginative faculty unguided and unchecked by any thing like a sober regard to facts. In the modern sense of the term, geology was not even thought of when astronomers began to measure and weigh the earth in order to ascertain its magnitude, its density and its form. It was not till after these questions had been long discussed, and pretty well determined, that scientific men commenced enquiring, by a careful examination of facts, into the interior structure of the globe, and the nature of the materials of which it is composed. It was then and not till then that the genius of Geology rose into existence, coming forth as from the depths of Eternity clothed in attributes of surpassing novelty and mystery, exciting in every contemplative mind, sentiments of unusual awe and admiration, opening for our perusal a new and mighty volume, "rich with the spoils of time," a wondrous history of life and death, and change, and ages past, compared with which all human records are but as a single isolated page.

The Science of Optics is another deeply interesting branch of knowledge, extensive in its ramifications and varied in its beauties as the light and hues of Heaven. But prior to the discoveries of Newton, the laws of light and colour were very imperfectly understood. There were, it is true, some scattered fragments of knowledge relating to refraction, and reflection, in the possession of a few scientific men, but there was no consolidated, comprehensive, generally received system of optical laws. Newton, we are told, while endeavouring to improve the telescope, procured a glass prism. With this he analyzed a beam of light, proved by the solar spectrum that it was composed of various coloured rays, explained the true philosophy of the rainbow, and from his own experiments defined and published an original system of optics, the great principles of which have been adopted by the whole scientific world. And who was it that first discovered the progressive motion and the relative velocity of light? It was an Astronomer. Yesand it was a man who was busy all his life in the invention and improvement of astronomical instruments, who first discovered the means of correcting, by a peculiar construction of lenses, the chromatic aberration of light. And in consequence of this discovery, we are now furnished with chromatic telescopes and achromatic microscopes, instead of those imperfect and now obsolete ones which were an incessant source of uncertainty and vexation to all who were in the habit of using them.

By the application of this discovery by Dollond to the construction of optical instruments, we now enjoy the advantage of being able to procure them so completely free from glare, and mistiness and false colours, as to enable us with ease, to ascertain the forms of structures of objects, which it was previously beyond the power of mortal faculties to discover.

Chemistry may also be cited as having made great advances within the limits of that period to which we have before adverted. In its present state of compresensiveness and exactitude, it no doubt approximates more nearly to Astronomy than any other branch of physical science. And though its obligations to Astronomy are not so palpably obvious to a casual observer, as those which are due from some other quarters; yet if attentively considered, they will be found to be neither few nor small. Certainly there existed nothing like a correct system of chemistry, till long after the time of Sir Isaac Newton. No one, it is presumed, would venture to deny this fact. Why, it was not till the 4th of August 1774, that Dr. Priestley discovered the existence of Oxygen Gas. Hear what a modern professor of Chemistry declares concerning Oxygen: "Of all elementary substances," says Professor Fownes, "Oxygen is the most abundant in nature, the most important to living beings, and that with which the study of the elements may be best begun." And yet, before the discoveries of Dr. Priestley, Oxygen was not known. A most extraordinary system of Chemistry, then, that must have been (had there been one) which ignored the existence of this all-pervading element. That Astronomy was the precursor of Chemistry, cannot be doubted, and there can be as little doubt that it was essentially advanced by that great and general impulse, which the discoveries of Newton gave to the whole circle of physical sciences. Nor is this all. The modern chemist, whilst prosecuting his refined and analytical researches, requires instruments, which upon due consideration will be found to derive much of their accuracy and value from the indirect influence of astronomical science. But this will perhaps be more distinctly evident when we come to discuss the connection of astronomy with weights and measures and philosophic instruments of various kinds.

As to Geography, every one must be aware of its great practical utility. But few words will be required to shew that for all its accuracy, and, therefore, for nearly all its value, it depends entirely upon astronomical science. For without maps and charts, and latitudes, and longitudes, what would any pretended system of geography be worth? If the existence of such a thing were possible, it would be as preposterous as a clock without hands, or rather without any figures or divisions on the dial plate. But how could any one construct a map or

chart, or lay down the true position of any object on the face of the globe without the knowledge of its latitude and longitude? If, for instance, any one wishes to ascertain his own latitude and longitude, what must he do? He cannot know it by intuition, nor has he reason to expect the indulgence of supernatural aid. He must either know enough of Astronomy to obtain it for himself, or he must apply to an Astronomer for the information. There remarks, brief, as they are, will be quite sufficient to indicate the reasons, why all our old maps and charts, whose dates are anterior to the prevalence of the Newtonian system of Astronomy, are so full of inaccuracies and positive errors, as to render them of no more value than so much waste paper, except as mere matters of antiquarian curiosity. Without Astronomy they never could amount to any thing more than guesswork or probable conjecture.

Chronology, also is of some practical importance in the affairs of mankind. Those who have given the most attention to it will not be the last to acknowledge that few departments of enquiry have presented a larger amount of puzzling problems for solution. Its apparent discrepancies have often proved vexatiously embarassing to those who were desirous of becoming the correct chroniclers of past events. In the earlier periods of civilization, no one was able even approximately to master it. To historical enquiries, it was an interminable quagmire, a slough of despond, and so it would forever have remained, had not astronomers directed their attention to the subject. Sir John Herschel very aptly compares the ancient calendar to a badly managed clock, which was sometimes forgotten to be wound up, sometimes set forward, sometimes put backward, to serve particular purposes or private interests. It is demonstrable, that the ancients knew neither the true length of the year, nor the time when it should begin or end. They tried hard to measure it, but they invariably made it too short or too long. At one time they made it consist of 355, at another of 455 days, but they were always wrong. The times and the seasons were perpetually getting away. The longer these discrepancies were neglected, the more glaring and complicated they became. At length the discordances were found so great, and so inconvenient, that it was absolutely necessary to attempt a reform. Julius Cesar determined to make an effort to set the matter right. For this purpose he obtained the assistance of Sosigines, the astronomer. Under his guidance, it was enacted that the year 46 B. C., should be called the "Year of Confusion," that they should commence their reckoning anew, and that another length of the year should be adopted. which would keep the calendar and the seasons more nearly in adjustment. This change dated from the year 45

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before Christ, which was the first regular year commencing on the first day of January. But Sosigines, though much nearer the truth than his predecessors, was not exactly right in the connection he applied, so that in about sixteen centuries it was found that the commencement of the year was again ten days wrong. In order to rectify this error, what is called the New Style was introduced by Pope Gregory in 1582. This New Style, however, was not adopted in England till the year 1752, about 20 years after the death of Sir Isaac Newton. At that time the error amounted to nearly eleven days. government authorities consulted Dr. Bradley, the celebrated astronomer, on the subject. He advised the adoption of the New Style, and was an active agent in its introduction, for which it is said his windows were broken, and he was in danger of being stoned by the populace. But notwithstanding opposition, the measure was carried, the law established, and since that period there has been no uncertainty concerning the beginning, the end, or the length of the year within the limits of a single second nor ever will be again as long as the science of astronomy shall endure.

Clocks, watches and chronometers are all practically useful instruments. In the present state of society they are indispensable. For their progressive improvement they are mainly indebted to the influence of Astronomy.

So again, with regard to Metrology, or the science of measures, this will again furnish a striking exemplification of the practical uses of Astronomy, for to this source we are indebted exclusively for the only exact and invariable standard of measures, whether of time, weight, space or capacity. As this is a point of considerable interest and importance to my argument, but not frequently discussed on occasions like the present, I must request the indulgence of your attention whilst I enter so far into particulars as to make myself clearly understood.

The earth revolves on its axis, once in 24 hours or in 86,400 seconds. The lapse of time required for this rotation, is always the same, and this is the only invariable phenomenon in the whole universe with which we are acquainted. All other things are in an incessant state of change, but this, as far as we know, has never presented any sensible evidence of variation. There is no change. But some one may be disposed to ask "How is this ascertained?" The fact may be verified by the following means: Suppose you possess a suitable telescope, well adjusted, and firmly fixed in the meridian, within the tube of this telescope there is placed a fine cross-wire (in reality it should be a line from a spider's web) stretched across the center of the field of view, and exactly perpendicular to the 50-VOL. VI.