SCHISLOSIIY AND SLATY CLEAVAGE 433 
granted two or three propositions which have been proved else- 
where. It isa fact that a simple uniform pressure acting upon 
Fic. 2.—Shear illustrated by deformation of a circle drawn on wire netting. 
a cube normally to two opposite faces is resoluble into forces 
which tend to produce? a cubical compression and two equal pure 
"Exactly one-third of the total pressure is employed in producing each of these 
three elementary strains whether they are of finite or of infinitesimal amount. 
