320 FRAGMENTS OF SCIENCE. 



produce her results; they are approaching more and 

 more to the domain of physics, and I trust the day will 

 soon come when we shall interlace our friendly arms 

 across the common boundary of our sciences, and pur- 

 sue our respective tasks in a spirit of mutual helpful- 

 ness, encouragement and goodwill. 



[I would now lay more stress on the lateral yield- 

 ing, referred to in the note at the bottom of page 316, 

 accompanied as it is by tangential sliding, than I was 

 prepared to do when this lecture was given. This slid- 

 ing is, I think, the principal cause of the planes of 

 weakness, both in pressed wax and slate rock. J. T. 

 1871.] 



