146 POPULAR LECTURES AND ADDRESSES. 



essential aeolotropy of crystals, and the seem- 

 ingly perfect isotropy of gravity. No finger-post 

 pointing towards a way that can possibly lead 

 to a surmounting of this difficulty, or a turning 

 of its flank, has been discovered, or imagined as 

 discoverable. Belief that no other theory of 

 matter is possible is the only ground for antici- 

 pating that there is in store for the world another 

 beautiful book to be called Elasticity, a Mode of 

 Motion. 



