206 Prof. Favre on the Origin of 



as the other facts I have mentioned, I cannot agree with Professor 

 Tait " that, so far as experimental facts were known in Newton's 

 time, he had the Conservation of Energy complete." In the case 

 of any other man it might appear ungenerous to look too closely 

 into claims to a scientific discovery put forward on his behalf by 

 well-meaning advocates, especially when there is not any better- 

 entitled competitor in the field ; but in the case of Newton, whose 

 head is already so thickly covered with laurels, this remark could 

 not apply. I cannot help thinking that the principle of the Con- 

 servation of Force, in its widest sense, was discovered by no single 

 person, but was only gradually evolved and developed ; and I am 

 mistaken if we are already in full possession of its meaning. 



Professor Tait protests against the allowing of any weight to 

 the opinion of John Bernoulli " on a question of this nature," 

 because he li seriously demonstrated the possibility of a perpetual 

 motion." I am not aware that, in point of theory, " perpetual 

 motion" is impossible; although, no doubt, " perpetual work" is. 

 But waiving altogether this point, would it not be possible also 

 on such a principle to impugn the value of any opinion of New- 

 ton — for instance, on the subject of light, on the plea that his 

 fundamental notion of the nature of light was wrong ? 



Like many others, I am anxious for the appearance of Pro- 

 fessors Tait and Thomson's long-promised treatise/; and in the 

 meanwhile the " Sketch of Elementary Dynamics," published 

 for the use of the students of Glasgow and Edinburgh, might 

 perhaps with advantage be made more accessible to students in 

 general than I have understood it to be. 



London, February 1865. 



XXX. On the Origin of the Alpine Lakes and Valleys. A Letter 

 addressed to Sir Roderick I. Murchison, K.C.B., by M. Al- 

 phonse Favre, Professor of Geology in the Academy of Geneva, 

 and Author of the Geological Map of Savoy*. 



Sir, Geneva, 12th January, 1865. 



I AM glad that you have asked my opinion of the new theory, 

 according to which the Alpine lakes have been excavated 

 or scooped out by glaciers ; and of that which also explains the 

 origin of the Alpine valleys by means of the erosion produced 

 by glacial action f. 



* Communicated by Sir Roderick I. Murchison, K.C.B., D.C.L., F.R.S., 

 &c. 



f A great many arguments against these theories have been advanced 

 in various memoirs, as in those of Mr. Ball (Phil. Mag. 1863, vol. xxv. 

 p. 81), Desor (Revue Suisse, 1860), Studer (Archives des Sc. Phys. et 

 Natur. 1863, vol. xix.), &c. However unwilling I may be to reproduce the 

 arguments which they have already employed, it is almost impossible not 

 to revert to them occasionally. 



