38 H. W. FairhoAiks — Contact Metamor-phism. 



would develop into further parting planes. Where these 

 cracks pass through the larger pebbles the latter do not appear 

 to be faulted in the least, so that we cannot attribute their 

 origin to the action of a shearing stress. The most probable 

 explanation which has occurred to the writer is that the part- 

 ings are due to contraction on cooling. This theory would 

 explain the local irregularities as well as the general parallel- 

 ism with the dike. 



Berkeley, California. 



