REVIEWS 295 



solved bv the granite, which holds many inclusions and also injects 

 itself into the rock in narrow veins — lit par lit — along its plains of 

 lamination or foliation, altering it intensely and at the same time 

 giving to it a granitic character. In the second half of the Bulletin 

 the author presents some observations on granites in general, more 

 especially in relation to their contact effects, reafifirming and some- 

 what enlarging upon the views put forward by him in 1887. He holds 

 that the conclusions arrived at by Rosenbusch and commonly held by 

 petrographers, that feldspar is not usually produced in contact zones 

 except in comparatively small amount by the diagenesis of the altered 

 rock, and that there is no transfusion of granitic material into the 

 invaded rock, although true of the individual contact zones investi- 

 gated, are not true of contact zones in general, but that there is fre- 

 quently developed immediately along the contact a zone in which 

 an intimate admixture of the granitic material with that of the 

 injected rock is a dominant characteristic. This admixture is brought 

 about in part by the injection of the granite in thin layers — lit par lit — 

 into the stratified rock parallel to its lamination, in part by a transfu- 

 sion in some obscure way by means of mineralizing solutions of the 

 elements of quartz and feldspar through the schists, causing these 

 minerals to crystallize out through the substance of the altered rock, 

 and in part by the actual solution of the injected rock in the granite 

 magma. In this zone, which in ordinary granite intrusions is usually 

 but a few yards in width, there can be found all the rocks characteristic 

 of the great regions of crystalline schists — mica schists, granulites, 

 gneisses, amphibolites, etc., formed by the action of the granite on the 

 ordinary sedimentary strata of the earth's crust. 



This zone, moreover, although often narrow as exposed, where the 

 deeper seated parts of the "appareils granitiques" are laid bare to our 

 studv bv the process of denudation, is found to become much wider 

 and often of great stratigraphical importance. Barrois is cited as 

 having found in Brittany cases where there has been an undoubted 

 transformation of whole districts of Cambrian schists into gneiss by 

 the process of " granitization " above referred to, it being possible to 

 follow bands of quartzite which resist the general " feldspathization " 

 from the margin of the area into parts of the district where the asso- 

 ciated schists have been completely transformed into gneiss. 



The work of Duparc and Mrazec, on the massiv of Mont Blanc is 

 also cited as affording conclusive demonstration of similar transforma- 



