We are now come hither from Rome, and hope to be in Paris by the end of June. I thank you for your letter, and desire you to believe that I can never grow strange to one, the goodness of whose acquaintance I have found by so much experience. But I have to write to so many, that I write to you seldomer than I desire; which I pray pardon, and esteem me Your most affectionate friend and humble servant THO. HOBBES. _Florence, Apr. (6)/(16) 1636._ My Lord and Mr. Nicholls, and all our company commend them to you. ----- Footnote 3: Probably George Glen, who was installed Prebend of Worcester in 1660, and died in 1669. Footnote 4: The History of the Sabbath. In two books. By Peter Heylyn. 4to. 1636. ----- IV. LETTER TO SIR CHARLES CAVENDISH.[5] HONORABLE SIR, [Illustration] The last weeke I had the honor to receave two letters from you at once, one of the 30 of Dec., the other of the 7^{th} of Jan., w^{ch} I acknowledged, but could not answer in my last. In the first you begin with a difficulty on the principle of Mons^r de Cartes, _that it is all one to move a weight two spaces, or the double of that waight one space_, and so on in other proportions: to w^{ch} you object the difference of swiftnesse, w^{ch} is greater when a waight is moved two spaces than when double waight is moved one space. Certenly de Cartes his meaning was by force the same that mine, namely, a multiplication of the weight of a body in to the swiftnesse wherew^{th} it is moved. So that when I move a pound two foote at the rate of a mile an howre, I do the same as if of 2 poundes I moved one pound a foote at y^e rate of a mile an howre, the other pound another foote at the same rate, not in directū, but parallell to the first pound. As if the wayt A B were moved to C D at the rate of a mile an howre, ’tis all one as if the waight A E were moved to F H at the same rate. Here is all the difference: this swiftnesse or rate of a mile an howre is, in the first case, layd out in the 2 spaces A G, G C, the latter, in the 2 spaces A G, E G. The first case, as like as if a footman should run w^{th} double swiftnesse endwayes, w^{ch} is y^e doubling of swiftnesse in one man: in the other, it is as if you doubled the swiftnesse by doubling the man: for every man has his owne swiftnesse. And so A H is the swiftnesse A G doubled, as well as A D. For that, that Mons^r de Cartes will not have just twice the force requisite to move the same weight twice as fast, I can say nothing. The papers I have of his touching that are in my trunk, w^{ch} hath bene taken by Dunkerkers, and taken againe from them by French, and at length recovered by frends I made: but I shall not have it yet this fortnight. In the meane time I am not in that opinion, but do assure