REVIEWS 299 



no attempt is made to follow out the changes undergone by a single 

 bed, and it is impossible to make out in how far the differences in 

 composition shown to exist, are primary differences in the composition 

 of the rocks analyzed. The chemical evidence adduced is, therefore, 

 by no means conclusive. The question also arises as to the ultimate 

 source of the enormous amounts of silica and alkalis required for the 

 conversion of hundreds of cubic miles of the miscellaneous rocks of a 

 sedimentary system into granite. 



It is furthermore a question as to how far dynamic action is respon- 

 sible for many of the phenomena described. When, for instance, a 

 schist is shattered and granite is intruded into the cracks and fissures, 

 masses of the invaded rock being found scattered through the granite, 

 and, after cooling, the whole complex is stretched or rolled out by 

 dynamic movements, as is usually the case in districts where ciystalline 

 schists occur, the injected arms of the granite, great and small, become 

 pulled apart and eventually appear as little discontinuous strings and 

 lumps of quartz and feldspar in the enclosing schists, following the 

 line of movement, while a schistose structure parallel to these strings 

 is given to the whole rock by the same movements. 



In certain parts of the Laurentian of Canada, schists and gneisses 

 are found full of such strings and lumps of quartz and feldspar, pre- 

 senting exactly the characters described by the French petrographers as 

 resulting from the granitization of sedimentary rocks. The Canadian 

 rocks, however, have undoubtedly been produced in the way just 

 described, every possible transition from the massive injection to the 

 foliated complex being observed in a hundred different cases. In the 

 Lepontine Alps, moreover, to the east of Mont Blanc, where the Schie- 

 ferhulle of the several protogine masses have been very carefully 

 studied by Heim, Schmidt, and many other observers, the phenomena 

 attributed to "granitization" by Duparc are everywhere considered to 

 be the results Of crushing under the influence of such movements, 

 with, in certain cases, the infiltration of secondary cracks and rifts by 

 materials deposited from ordinary terrestrial waters, which in such 

 positions would probably be more or less heated. Even in the Saxon 

 Granulitgebirge, cited by Michel-Levy as a case where transference of 

 material could be distinctly observed, and where certainly the granulite 

 does seem to have eaten its way into the schists, only however for a 

 short distance back from the immediate contact, the appearance pre- 

 sented bearing a striking resemblance to that, very familiar to the tyro 



