A Michigan PrcJiniinary Section. — Graban. 189 
The thickness of the shale has not been ascertained. The 
Hmestone unclerhes the shaly hmestone of Loc. 14, and if the 
correlation of the latter with the "shale" of stratum 9 is correct, 
this limestone and underlying- shale are tO' be correlated with 
strata 10 and 11 of the Churchill well, respectively. 
Some of the sink-holes are 50 or more feet in depth, but 
their sides are difficult to examine, since they are usually per- 
pendicular, or else covered by talus. 
Shales w^ith fossils of the Alarcellus type are said to be ex- 
posed in the vicinity of Bell, but thev have not been seen. A frag- 
ment, however, containing a characteristic Marcellus Chonetes, 
and obtained from this exposure, has been seen. The location 
is along the strike of the shales out of which Grand lake is 
carved. 
Rensselaer Polytechnic Institntc, May. iqoi. 
EDITORIAL COMMENT. 
THE ARCHEAN OF THE ALPS. 
The very able and interesting volume by Duparc and Mrazec, 
which has lately come to our notice, is a valuable contribution 
to the geology not only of the Alps, but of the Archean of 
every country so fortunate as to have any Archean rocks. 
The investigation was carried through seven years. It may, 
therefore, be presumed that the results reached are the best 
that can be attained by the intelligent use of all methods of 
modern geological research. Careful and extended field work 
was supplemented by chemical and petrographical laboratory 
study. 
The monograph abstracts the opinions of former geologists 
as to the nature and relations of the Mont Blanc massif, but 
carries the examination into greater detail than any predecessor, 
reaching, therefore, somewhat different conclusions. It is 
specially detailed and complete on the relations of the granite 
(called protcgine, a term which the authors would discard) to 
the schists, and throughout all its descriptions it is illustrated 
by half-tone reproductions of photographs of Alpine scenes. 
*Kecheivhes geologiqiics (>t ixtrographir|iies sur le massif du Mont-Blanc. 
I'ar I/Oiiis Duparc et' Lmlnvic .Miazec. ii4 plates, pp. li"-8, (piarto. (leneva. 
1S'J8. (Mem. Soc. I'hys. el Hist. Nat., Tome xxxiii, No. 1) 
