1 6 P Ori' EAR EECTl'RES AND ADDRESSES. 



we might expect it would altogether subside ; and 

 in his theory of the tides, he treats the motion 

 of the sea altogether as a motion of oscillation. 

 There then is a tacit admission of the fact of 

 resistance. But that tidal resistance influences 

 the rotation of the earth, or, by reaction, the 

 motions of the moon and sun, Laplace does not 

 explicitly state. The modern theory of energy 

 was imperfectly understood by Laplace and 

 range. Lagrangc, it is true, gave a foundation 

 for the mathematical treatment of Dynamics, in 

 which the theory of energy was the one great 

 principle ; but he did not point out the applica- 

 tion of the theory of energy to some of the 

 consequences which now, in the present state of 

 science, interest us perhaps more than any 

 other conclusions which have been drawn from 

 mathematical and physical reasoning. I am there- 

 tort: entitled to speak so far of the science of 

 LS modern, although it was from Toricelli, 

 Xewton, John r>eniouilli, and Lagrangc, that we 

 have le. imed the abstract dynamical principles 

 of the .science of energy. Kven this abstract 



