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tion, while the gneissic zone about the granulite of the Saxon Granu- 

 litgebirge is cited as another case in point. It is beHeved that the 

 granite magma first rises along lines of fracture in the crust. Its 

 presence leads to a heating of the rock into which it is injected, and 

 its intrusion is accompanied by a ^'circulation intense'''' of mineralizing 

 fluids, probably rich in alkalis. These produce at first a transference 

 of quartz from one part of the mass to another and the development of 

 biotite, which is a marked feature in contact zones. Then follows 

 "feldspathization," which commences by the development of little 

 strings of quartz and feldspar following for the most part the schistos- 

 ity of the invaded rock, and which grow in size until the whole mass 

 of the schist is transformed into granite, the texture of the schist being 

 broken down and its elements set in motion to form with the trans- 

 fused material new combinations. The granitic magma or emanations 

 thus slowly dissolve, alter or incorporate, whichever we may choose to 

 call it, the wall rock, transforming it first into a gneiss, then into a 

 gneissic granite, and finally into a granite. The original intrusion thus 

 slowly enlarges its boundaries and increases its volume. 



This process, we are told, is at work wherever granitic magmas 

 come in contact with clastic rocks in the deeper parts of the earth's 

 crust, and it is thus that, as before mentioned, the crystalline schists 

 are produced. The granite does not therefore, as Suess has supposed, 

 fill great cavities in the earth's crust which have been produced by tan- 

 gential stresses, thus giving rise to batholites, but starting from some 

 line of fracture eats its way into the surrounding rocks and develops 

 itself largely at their expense in the way above described. 



According to Professor Duparc and his associates, this process of 

 granitization plays a very important role in the development of the 

 crystalline rocks of the Mont Blanc massiv. This massiv has usually 

 been considered as composed of protogine, that is of a somewhat altered 

 granite, massive in the center and progressively more gneissic or schis- 

 tose as the outer portions are approached, the whole enveloped by a 

 mantle of mica schists. These mica schists contain bands of amphib- 

 olite, eclogite, and other similar rocks found in corresponding posi- 

 tions about other protogine masses elsewhere in the Alps. 



Messrs. Vallet and Duparc have however found that the central part 

 of the massiv is composed largely of various micaceous gneisses and 

 crystalline schists, associated with and invaded by the protogine and 

 even passing into a protogine gneiss. Some of these included rocks 



