470 Dr. C. K. Akin on the History of Force. 



them by assuming the latter mineral to differ from the former 

 only by containing H 2 less, and by the presence of 1 atom 

 of S in lieu of 1 atom of O: — 



C 4o H 62 3 + H 2 0. . . , Retinite. 



Cio H 62 2 S Tasmanite. 



To suggest a rational formula for the remarkably complex 

 molecules of retinite and Tasmanite may seem premature ; but it 

 is possible that in these minerals we have the hydrated oxide 

 (retinite gives off water when heated) and the anhydrous sul- 

 phide respectively of an oxygenated radical, C 20 H 31 — 



C 20 H 31 

 C 20 H 31 



C 20 H 31 



C 20 H 31 



These minerals may be derivatives of a turpentine, C 20 H 32 ; 

 or the radical I have assumed them to contain may be a homo- 

 logue of benzoyle, 



C 7 H 5 O-fl3CH 2 = C 20 H 31 O. 



n O f ^) + ^1 Retinite. 



hq >S Tasmanite. 



LVIIL On the History of Force. By Dr. C. K. Akin*. 



IN the Number of the Philosophical Magazine for October 

 last (p. 289), Professor Guthrie Tait repeats an assertion 

 already made by him upon two previous occasions, first in the 

 Philosophical Magazine (see vol. xxv. p. 429, 1863), and next 

 in the Proceedings of the Royal Society of Edinburgh (see 

 No. 59, p. 122), that " Newton had completely enunciated the 

 Conservation of Energy in ordinary mechanics ;" and in another 

 portion of the same Number of this Magazine (p. 311), Professor 

 Bohn cites passages from the writings of Descartes and John 

 Bernoulli bearing on the same question of the Conservation of 

 Force also. For nearly two years, I have been engaged at inter- 

 vals in collecting materials for a History of the Philosophy of 

 Force, but which circumstances now oblige me to lay for a while 

 aside. I am thus induced to publish meanwhile part, at least, of 

 what little I have hitherto discovered that is new or interesting, 

 in the Philosophical Magazine ; for doing which the publications 

 above referred to at present afford me an additional incentive. 



I. On the Conservation and Conversion of Force. 

 1. Prof. Tait rests the claims which he advances in behalf of 

 Newton, on the following passage from the scholium to the Third 

 Law of Motion, in Newton's Principia : — 



* Communicated by the Author. 



