Prof. Bohn on the Conservation of Energy. 311 



Several other points raised by Sir Roderick in that part of his 

 Address that relates to physical geology, glaciers, and icebergs 

 remain to be discussed. I have entered, however, on this argu- 

 ment with great reluctance, and, unless circumstances again con- 

 strain me, I shall leave the remaining questions untouched. 



XXXYI. Historic Notes on the Conservation of Energy. 

 By Professor Bohn. 



To Professor Tyndall, Esq., F.R.S. 



I READ your " Notes on Scientific History"* with great plea- 

 sure and satisfaction. 1 agree perfectly with all you say 

 respecting Mayer's researches as compared with those of others ; 

 in some respects, indeed, I am inclined to go further than you do. 

 Seven years ago I studied the history of the principle of the 

 Conservation of Energy, and arrived at the same conclusion, with 

 respect to the modern development of this theorem, as the one 

 for which you so ably and warmly contend. Your recent disin- 

 terested advocacy of Mayer's claims, and my own conviction 

 that historic truth is the sole object of your research, inspire the 

 hope that the following remarks will be found worthy of atten- 

 tive perusal. 



Descartes, so- far as 1 know, was the first to give expression to 

 the thought that whatever is not material must necessarily be 

 indestructible. This non-material something he called u Force," 

 a word which subsequently had, for a long period, divers and 

 consequently vague meanings. 



In Descartes's Principia Philosophies (Pars II., § xxxvi.) we 

 find the following : — " Deum esse primariam motus causam et 

 eandem semper motus quaDtitatem in universo conservare. 



ft Motus natura sic animadversa, considerare oportet ejus 

 causam, eamque duplicem : Primo scilicet universalem et pri- 

 mariam, quae est causa generalis omnium motuuni qui sunt in 

 mundo; ac demde particularem, a qua fit, ut singula? materia? 

 partes motus, quos prius non habuerunt, acquirant. Et gene- 

 ralem quod attinet, manifestum mihi videtur illam non aliam esse, 

 quam Deum ipsum, qui materiam simul cum motu et quiete in 

 principio creavitf, jamque per solum suum concursum ordinarium, 

 tantundem motus et quietis in ea tota quantum tunc posuit 

 conservat. Nam quamvis ille motus nihil aliud sit in materia 

 mota quam ejus modus ; certam tamen et determinatam habet 



* Phil. Mag. S. 4. vol. xxviii. p. 25. 



t Phil. Mag. S. 3. vol. xxiii. p. 442 (1843) : Mr. Joule, " That the grand 

 agents of nature are by the Creator's flat indestructible." 



