Editorial Comment. 191 
He reached the conchision that the massif of ■Nit. Blanc forms a. 
synchnal pinched between two faults, but later in consequence 
of an excursion with Michel Lev}' he recognized the eruptive 
nature of this rock. The Italian geologists, with Zaccagna at 
the head, consider it also as a particular facies of primitive 
gneiss. Amongst them this opinion is strongly rooted, for in 
1893, in his "Geology of the province of Turin," Baretti uni- 
formly considers the protogine as a lower term of the crvstal- 
line rocks. With Gerlach the protogine of Alt. Blanc is mani- 
festly an eruptive rock. Its apparent stratification is a result 
of compression. Michel Levy shares the opinion of Gerlach, 
as to the eruptive and intrusive nature of this rock. He 
chiefly bases his argument on the contacts of the rock with its 
crystalline mantle, and also upon the phenomena of injection 
and of metamorphism which it develops there. The authors 
themselves, in their earlier papers, have started from the same 
point of view and have insisted chiefly on the metamorphism in 
question. It can be stated, in general therefore, that, with the 
exception of the Italian geologists, there seems to be at present 
an approach to agreement on the eruptive nature of the pro- 
togine of Mt. Blanc. 
But having agreed that it is an eruptive those who have 
studied this protogine seem not to have accounted for its origin, 
nor for the terms that intervene loetween the normal and com- 
pletely developed granite and the schists into which it is so 
plainly intruded. What is the cause of Nos. (2) and (3), the 
schistose granite and the gneissic granite ? The former has cer- 
tain suggestive points of petrographic likeness to the mica 
schists. It runs imperceptibly into the gneissic granite. The 
gneissic granite (No. 3) cannot be separated, in the field, from 
the protogine (No. 4). 
It will be instructive to gather together some of the evi- 
dences, given by the authors,, that go to show that these four 
terms are but steps in one great event, phases that depend on 
incompleteness of the process, or on dift"erence of original com- 
position and structure in an original sedimentarv r(x:k. 
The authors say (p. 20) : ( i )The granitic type of the proto- 
gine is light colored, with variable grain, often very fine, with 
black mica evenly disseminated, with great rcgularit\-, in the 
mass. The gneissic type is usually of a darker color, greenish,. 
