127 



containing additional information in regard to the Mastodon 

 bones, on which a communication from him was read at the 

 last meeting. 



In the description of the bones communicated to the Society at 

 that time, Mr. Maxwell omitted to mention one circumstance, which 

 struck him as peculiar. The back grinders, which had not yet cut 

 through, were placed so far back, that they could be of no use to the 

 animal in that position, and it appeared evident, that only two grind- 

 ers could be in use at the same time, and that as the forward ones 

 were worn out they would be shed, and their place supplied by those 

 behind pushing forward ; — a beautiful provision — Mr. Maxwell con- 

 ceives — for an animal of long life subsisting upon hard substances. 



Professor Henry, of Princeton, made an oral communication 

 in regard to some speculations in which he had indulged, re- 

 lative to the classification and origin of mechanical power. 



He stated, that he was indebted for the origin of this train of thought 

 to some remarks made by Mr. Babbage in his work on the economy 

 of machinery, and to the late researches of the German and French 

 chemists on the subject of vital chemistry ; indeed, all the views con- 

 tained in the communication, might perhaps be found in detached 

 portions in different works; but he believed, that they had never be- 

 fore been brought together and presented as a whole. 



He defined mechanical power to be that which is capable of over- 

 coming a constant resistance, and of producing a continued motion ; 

 or, in the language of the engineer, it is that which can be employed 

 to " do work." It is here used in a more restricted sense than force, 

 which is applied, as a more general term, to whatever tends to pro- 

 duce or resist motion. The following list of mechanical powers, 

 he believed, would be found to include all the prime movers em- 

 ployed at the present time, either directly or indirectly, in producing 

 mechanical changes in matter, and all these could be referred to two 

 sources : — 



C Water power, ^ 

 Class 1st. < Tide power, > Referable to celestial disturbance. 

 ^ Wind power, ) 



C Steam and other '^ 



Ch 2d i powers developed ! Referable to that which is call- 



' j by combustion. j ed vital action. 



L Animal power. J 



