418 PHILOSOPHICAL TRANSACTIONS. f^ANNO IJOS. 



attraction of matter. That there is a vacuum, is plain from the motion of 

 bodies: geometricians demonstrate the divisibility of quantity from the nature 

 of continued quantity: and experience proves that matter has an attractive force. 

 From the first two principles follows: 



Theorem 1. — Any particle of matter, however small, may fill a space how- 

 ever large, in such a manner, as that the diameters of all the pores and vacui- 

 ties in it, may be less than any given right line; or that the distances of the 

 particles from each other may be less than a given right line. 



Theorem 2. — Two bodies njay be given of equal bulk, however unequal in 

 weight and density (i. e. quantity of matter) the sums of whose vacuities or 

 pores may also approach to a ratio of equality. Let there be, for instance, a 

 cubic inch of gold, and another of air: then though the quantity of matter in 

 the cube of gold exceed 20000 times that in the cube of air; yet it is possible 

 that the vacuities in the former may be almost equal to those in the latter, viz. 

 that the vacuities in the gold may be to the vacuities in the air; as QQQQQQ to 

 lOOOOOO. 



Theorem 3. — ^The particles which constitute water, air, or such like fluids, if 

 they touch each other, are not absolutely solid, but consist of other particles, 

 that contain vacuities and pores. The most minute and absolutely solid particles 

 of bodies, that is, such as have no vacuities at all, may be called particles of the 

 first composition : the moleculae arising from the coalescence of several of these 

 particles may be denominated particles of the second composition: and again 

 the masses made up of several of these moleculae, may be called particles of the 

 third composition ; and so on, till at length we come to particles which consti- 

 tute the ultimate composition of bodies, and into which they may be ultimately 

 resolved. That matter is endued with an attractive force, by which its particles 

 mutually attract each other. Sir Isaac Newton first deduced from the phaeno- 



them in their passage to New England in America. And soon after his return, in 1710, on the death 

 of Mr. Caswell, Savilian professor of astronomy at Oxford, he was chosen to succeed him. About 

 the year 1711 several objections being urged against Newton's philosophy, in support of Descartes's 

 notions of a plenum, M. Keill presented to the Royal Society a paper on the Rarity of Matter, and 

 the Tenuity of its Composition. And while engaged in this controversy, he was apointed decipherer 

 to queen Anne, an office which he held also under king George the First, till 171 6. Other ingenious 

 compositions of his are also found in the Philos, Trans. In 1713 the university of Oxford conferred 

 on Mr. Keill the degree of M.D ; and two years after, he published an edition of Commandine's 

 Euclid, with a Iditions of his own. In 1718 came out his Introductio ad Veram Astronomiam; an 

 English edition of which was also published in 1721, entitled. An Introduction to the True Astrono- 

 my: or, Astronomical Lectures, read in the astronomical school of the university of Oxford. Thii . 

 was Dr. Keill's last gift to the public j being this summer seized with a riol«D' fever, which put a 

 period to his useful life, Sept. I, in the 50th year of his age. 



