6o2 



CLARENCE N. FENNER 



transition is produced from the hornblendic or biotitic gneiss or 

 schist, in which foHation is prominent, through gradations in 

 which the dark minerals become less and less noticeable and the 

 proportion of granite increases, up to a type in which little or 

 no parallelism of structure can be perceived. In other places 



Fig. 7 



the dark minerals appear to have been taken up or digested by the 

 magma and to have crystallized out again in large blades. Even 

 in the latter case it is not always certain that perfect solution has 

 been effected at any one time. The process may have been rather 

 in the nature of a chemical reaction with the original minerals or 

 the solution and redeposition of a portion of the material at a time, 

 leaving the general relations undisturbed. This possibility is 



