[39] M. Delambre maintains that these views of Borelli are only those of Kepler slightly modified. Newton and Huygens have attached to them a greater value. The last of these philosophers remarks, “Refert Plutarchus, fuisse jam olim qui putaret ideo manere lunam in orbe suo, quod vis recedendi a terra, ob motum circularem, inhiberetur pari vi gravitatis, qua ad terram accedere conaretur. Idemque ævo nostro, non de luna tantum sed et planetis ceteris statuit Alphonsus Borellus, ut nempe primariis eorum gravitas esset solem versus; lunis vero ad terram, Jovem ac Saturnum quos comitantur.”—Huygen, Cosmotheor, lib. ii.; Opera, t. ii. p. 720.
[40] Hist. de l’Astronomie aux Dix-huitieme Siècle, p. 9.
[41] “But for the duplicate proportion, I gathered it from Kepler’s theorem about twenty years ago.”—Newton’s Letter to Halley, July 14, 1686.
[42] Whiston asserts that this cause was supposed by Newton to be something analogous to the vortices of Descartes.—See Whiston’s Memoirs of himself, p. 231.
[43] Waller’s Life of Hooke, p. 22.
[44] Ibid.
[45] July 27, 1686, Biog. Brit. p. 2662.
[46] Commercium Epistolicum, No. 7.
[47] This Scholium is added to Prop. iv. lib. i. coroll. 6.
[48] In writing to Flamstead, Newton requests from him the long diameters of the orbits of Jupiter and Saturn, that he “may see how the sesquialteral proportion fills the heavens.”