terrestrial meridian, and of the pendulum, multiplied in different parts of the globe, of which France gave the example, by measuring the whole arc of the meridian, which crosses it, and by sending the academician to the north and to the equator, to observe the magnitude of these degrees, and the intensity of the force of gravity. The arc of the meridian, comprised between Dunkirk and Barcelona, determined by very precise observations, and forming the base of the most natural and simple system of measures; the voyages undertaken to observe the two transits of Venus over the Sun's disk, in 1761 and 1769, and the exact knowledge of the dimensions of the solar system, which has been derived from these voyages; the invention of achromatic telescopes, of chronometers, of the sextant and repeating circle, the discovery of the planet Uranus, by Herschel, in 1781; that of its satellites, and of two new satellites of Saturn, due to the same observer, all the astronomical theories being brought to perfection, and all the celestial phænomena, without exception, being referred to the principle of universal gravitation:-these, with the discoveries of Bradley, are the principal obligations which astronomy owes to England, which, with the preceding, will always be considered as constituting the most glorious epoch of the science. [La Place, Exposition du Systême du Monde.]

CHAPTER IV.

GENERAL NOTICES ON ASTRONOMY

To the preceding observations of La Place, the Editor of the

present work has thought right to subjoin the following singular or learned opinions of several of the most esteemed writers on the subject.

Professor Playfair, in an article inserted in the Edinburgh Philosophical Transactions, supports the very high pretensions of the Bramins to Astronomy, and conceives that they are in possession of some observations not less than five thousand years old. Mr. Costard, in a paper on the Chinese Chronology and Astronomy, print

ed in the Transactions of the Royal Society for 1747, and Mr. Bentley, in Vol. VI. of the Asiatic Researches, offer cogent arguments against any such antiquity of Astronomical knowledge in the East: the latter indeed goes so far as to make the principal tables of the Bramins, which they call Surya Siddhanta, not more than about 733 years old.

Newton thinks that the constellations were arranged by Chiron when the solstitial and equinoctial points were in the middle of the respective constellations. Phil. Trans. for 1725.

Mr. Wall, in a paper on astronomical symbols, printed in the Manchester Memoir, Vol. I. 243, derives (Mercury), from the

caduceus; and spear;

(Venus), from the sistrum; (Mars), from the shield (Jupiter), from Jr, the contraction or first and last letters of the word; (Saturn), from the sickle. Frisch, however, derives 2 from lightning with the eagle.

Alexandre and Baliani thought the Earth revolved around the Moon. Marian.

In the account of Gail's Memoir ou Synesius's Astrolabe, Maps are attributed to Anaximander 600 years before Christ. M. Inst. V.34.

According to Plutarch, Heraclides and Ecphantus attributed to the Earth a diurnal motion only.

Astronomy was introduced into Spain by the Moors in 1201.

The Mexicans when discovered by the Spaniards had years of 365 days, and added 12 days at the end of every period of 52 years. Robison. Young's Nat, Phil.-Editor.

CHAPTER V.

THE CELESTIAL WORLD DISCOVERED; OR, CONJECTURES CONCERNING THE INHABITANTS, PLANTS, AND PRO

DUCTIONS, OF THE WORLD IN THE PLANETS;

Written in Latin by CHRISTIANUS HUYGENS, and inscribed to his brother CONSTANTINE HUYGENS, late Secretary to his Majesty King William. 8vo. with five cuts of Illustration,

THE ingenious author of this discourse, having spent much time, and taken great pains in making celestial observations and discoveries by telescopes of the largest sizes, and other instruments, and having moreover acquainted himself with the latest and best observations and discoveries made by other modern Astronomers; and having well weighed and considered the import and significancy of them, comes in this book to acquaint his brother the heer Constantine Huygens, (who was also a great lover of these inquiries, and who was the person that furnished him with the excellent telescopes he made use of, wrought with his own hand, wherein he had for his diversion acquired an extraordinary art and dexterity, unknown to any besides himself) and by the publication of it, if he thought fit likewise to acquaint the learned world, what upon the result of all, his opinion and belief was concerning the form, structure, and fabrick of the universe, or the whole visible world, and the reasons and arguments that induced him thereunto, which he hopes may seem reasonable enough to men skilled in geometrical, and astromical sci. ences; such as he wishes his readers may be. But because he was well aware that many of them might be persons of differing qualifi cations, and such as could not, or would not understand the cogency of them, or from prepossession would endeavour to carp at, and make arguments against the whole doctrine there delivered, therefore he endeavours to enumerate and obviate such as are most likely to be produced for that end. The first of which he conceives, may be of such as are ignorant of mathematical knowledge, who will be apt to represent it as a whimsey only of a disturbed brain, they

thinking it impossible to measure, or any wise to be ascertained of the magnitudes and distances of the celestial bodies; and as to the earth's motions they look on them as fictions, and not capable of being proved to such he answers, that he does not assert those things as absolutely demonstrated but rather as probable conjectures, and that he leaves every one free to judge of them as they please. And to such as may think them useless, since they are only conjectural, he answers, upon the same account, all other physical knowledge may be rejected, since that also for the most part is but conjectural; and yet we know the studies of those things are very commendable, and afford great pleasure, satisfaction, and benefit, even to such as think them contradictory to holy writ, to suppose other worlds, or animals then those of the earth; because such are not mentioned in the history of the creation. He thinks there has been enough said to shew that the description of the creation in the Bible, was only with relation to the earth, and not at all with respect to the other parts of the world, then what where here visible; nor can it be detrimental to religion, but will be rather, as he conceives, a means to make men have a lesser esteem of these earthly things, since they are but small, with respect to the other world, and to have a greater veneration and adoration of that wonderful wisdom and providence which is universally displayed through the whole fabrick of the universe. As to the form and disposition of the whole, and of the parts of this universe, he agrees with the system of Copernicus; for the better explication of which he hath added two figures, the first of which shows their order and positions, and the second their comparative magnitudes. And because by reason of the smallness of these figures, the true proportions could not be sufficiently exprest, he has added a particular explication, expressing in numbers, the distances of their orbs from the sun in the center, and the times of their periods in them: next of their particular magnitudes and so of their proportions to each other, and to the body of the sun. And since it hereby appears that the earth is moved about the sun, as well as the other planets, (which all the best of the modern astronomers do now believe, and none but such as are of a more dull apprehension, or are otherwise over powered by their superiors, do deny, or make any scruple positively to assert) and that those planets are enlightened by the sun in the same manDer as the earth is, and some of them, ash and 24, have their own

moons, or secondary planets moving about them, sometimes eclipsing them, and eclipsed by them, as the earth also is by its moon, and that some of them are much bigger, as well as some others smaller than the earth; and so that the magnitudes are not proportioned, either according to their order or their distance; since also they are observed to have the same kinds of motion, both annual and diurnal, therefore he thinks it very probable that they do resemble the earth also in other qualifications; for that we have no argument to the contrary why they should not, nor is this way of reasoning from the agreement in some to a like agreement of other precarious, since it is the most usual method of discovering the insensible parts of the world, by their similitude to the more sensible, as in anatomy we judge of the parts of a creature, by the similitude we find they have to the parts of some other before known. From this topic therefore he thinks we may safely conclude that the other planets have solid bodies, and gravity towards their centers, as the earth hath since, we find them to have the same figure, and the same motions, and the same concomitants, and that they have atmospheres and air, and water, &c. Aud since it would be too great a depretiating of them, and a too much overvaluing of the earth, to suppose them not to be likewise adorned with the more admirable productions and fabricks of plants, and animals, which more evidently manifest the wisdom and design of the divine architect, which we find the earth to be enriched and beautified with. But to suppose them only lifeless lumps of matter, as earth, water, &c.; or vast deserts, barren mountains, rocks, &c. This he says would sink them too much below the earth in beauty and dignity, which this method of reasoning will in no wise permit. He conceives therefore we must suppose and believe them to have animals as well as the earth; and so of necessity plants for their nourishment. And these possibly not much different from those we have, both as to their outward form, and as to their internal structure, and as to their method of production, or propagation, and their increase or growth. And that if there be any difference, most probably it must arise from the differing distances of those globes from the sun, which is more likely to affect the matter than the form. Wherefore though we cannot be ascertained what these differences are, yet we may reasonably conclude, that they are composed of solids and fluids; for that the production and nutrition of these animals must be made