Editorial Comment. 197 
different manners — a suggestion, liowever, which seems to 
have Httle vaHdity since (p. 87) they form the cement of a 
conglomerate constituted of blocks and pebbles more or less 
rounded of granulyte and of protogine. There may, however, 
be some error of observation in correlating this conglomerate 
with the porphyry in general, since (p. no) the contact of the 
porphyries with the protogine is said to be fresh and distinct, 
but often accompanied by intervening laminated or micaceous 
rock, and by the alteration of the protogine to aplyte and the 
occurrence of great numbers of veins of granulyte, in the pro- 
togine — features that seem to indicate the later date of the pro- 
togine. How it could be done the authors do not indicate, but 
they assume that the porphyries (here included this great series 
of sericitic rocks with their variations) have been subjected, 
locally, generallv and wholly, throughout their mass to dynamic 
forces more or less violent, which, when intensified, were able 
to destroy and grind up entirely the minerals of the first con- 
solidation and tO' transform the rocks into true schists with a 
sericitic detrital aspect. Only calling to mind the authors' re- 
jection of such a process in the case of the crystalline schists 
of the western part of Mont Blanc, for the origination of 
those schists from the crushing of the protogine, it is well to 
state hare that according to studies carried out on similar rocks 
in northern Minnesota, these rocks are of oceanic origin, large- 
ly detrital, varying to graywackes, and that they originated 
cotemporaneously with others that are now mica schists, and 
that probably when they are consecutively traced from the 
southeastern flanks of Mt. Blanc they will be found to be insep- 
arable from the mica schists which are penetrated by the gran- 
ite of Mt. Blanc, as in the Val Ferret (p. 131), and that in 
general they escaped the profound metamorphism of the Alpine 
Archean by reason of their geographic location with respect to 
the center of greatest dynamic activity. 
As has been stated, the authors everywhere recognize the 
fact that the mica schists, the gneiss and the protogine (or 
granite) are linked by insensible gradations in arcal relations 
and in petrographic and chemical association into one con- 
tinuous petrologic series, the granite and the schist being the 
extremes. Not only are there such interlocking gradations, 
but there are similar major features that help to form the com- 
