372 FKAGMENTS OF SCIENCE. 



in a spirit of mutual helpfulness, encouragement and 

 goodwill. 



[I would now lay more stress on the lateral yielding, 

 referred to in the note at the bottom of page 368, 

 accompanied as it is by tangential sliding, than I was 

 prepared to do when this lecture was given. This sliding 

 is, I think, the principal cause of the planes of weak- 

 ness, both in pressed wax and slate rock. J. T. 1871.] 



