272 Review of Recent Geological Literature. 
ulitic masses do not exhibit such modifications ; it fails to be seen only 
in some apophyses of the more important deep-seated masses : 
The modification of granulyte at contacts is not due, in the Morbihan, 
to molecular changes between the eruptive magma and the enclosing 
rock, but simply to the cooling, which acts upon the orientation of the 
elements of granite, upon their manner of grouping and the order of 
their crystallization . 
Two principal cases result from our study ; according as the contact 
observed is parallel or perpendicular to the direction of the enclosing 
rocks : in the cases of parallel contact the prevailing modification is 
the passage from a granular granulyte to a porphyroidal granulyte, 
the leading elements being arranged in fluidal lines ; in the cases of 
perpendicular contact there can be seen generally the development of 
aplytes, fine, granular, massive rocks of which the crystalline ele- 
ments present regular geometric outlines. 
The consideration of these two cases shows that the endomorphous 
changes of granulyte depend on the surroundings, such as a chemi- 
cally inactive agent, acting difi'erently in the presence of heat and 
pressure. We should note that this conclusion should be applied 
simply to the granulytes of Morbihan ; it would be incorrect and even 
entirely false to generalize from it : we shall show this in describing 
the granitites of the region. 
Notwithstanding the difi'ei'ence, quite considerable at first sight, be- 
tween the porphyroidal granulytes and the aplytes, it is easy to recog- 
nize in them homologous formations, equally characterized by their 
idiomorphic structure. 
The structure of these contact rocks, compared to that of massive 
granular rocks from the center of the masses studied, shows that the 
crystallization of the elements of granite is carried on progressively, 
and that, beginning in the vicinity of the walls, (salbandes) , in a mass 
still in movement, it advances toward the interior of the mass across a 
magma in repose, without showing any more trace of flowage. 
The schistose granulytes of the Morbihan, rocks having a gneissic struc- 
ture, fine or coarse, are confined, like the preceding, to the periphery 
of the granulitic masses, and are nothing but the preceding rock them- 
selves, aplitic, granular or porphyroidal, mechanically metamorphosed. 
The micaceous lamellpe, torn and stretched, the feldspar crystals 
broken and blunted, attest powerful mechanical forces experienced by 
the rock. These minerals were afterward recemented by sheets and 
fibers of sericitic white mica, sometimes of black mica, and by films of 
secondary granular quartz formed from the broken debris of the origin- 
al constituents. 
Finally the gradual passage from the schistose granulytes to the 
granular granulytes, when they are followed from south to north, 
brings out, as elsewhere, the general fact, recognized by us, of the 
localization of the schistose granulytes on the southern flanks of all 
the masses of granular granulyte in the Morbihan, and allows the ref- 
