6o8 CLARENCE N. FENNER 



apart and even sharply contorted in minor folds, but brecciation, 

 or large disturbances of any sort appear to have been lacking. 

 Where the invading magma entered in large quantity, movements 

 of considerable amount within its mass appear to have occurred. 

 One body having a width of nearly 200 feet was observed, in which 

 the infrequent inclusions had a somewhat more blocklike form than 

 in general and a variable strike, approaching at times a right angle 

 to that which generally prevails, implying differential movements 

 within this large mass of liquid. The dark bands shown in Fig. 14 

 lie somewhat to the northeast of this main mass of granite and 

 trend directly toward it, and are bordered on either side by tongues 

 or offshoots from it. As they approach the granite mass in their 

 prolongation beyond the lower left-hand side of the photograph 



-jS=^. r-- 



FlG. 13 



they curve much more toward the left and are finally cut off or 

 dissolved by the granite. 



In the process of igneous intrusion illustrated at this locality 

 it is quite certain- that nothing in the nature of "stoping" was a 

 factor of importance. It is not intended to imply, however, that 

 such a process may not have been the effective means of intrusion 

 in other instances. It is assuredly true that in different localities 

 and under varying conditions the mechanics of intrusion have been 

 radically unlike. 



Several of the features which have been described argue against 

 the probability that the dark bands represent squeezed-out differ- 

 entiates in a mass of magma. Probably the most impressive 

 evidence in this connection is the sudden termination of certain 

 sharply defined bands, with indications of corrosion at the end, 

 which was frequently observed. The same phenomenon is opposed 

 to the idea that the elongated structure of the bands of schist is 



