246 Reviews—Dr. Barrois’ Geology of Asturias, ete. 
investigations which seem wholly based upon the microscope. We 
should then Jearn how far the “white mica” and chlorite” of Dr. 
Barrois are identical with the “sericite” and ‘‘chloritoid” of Mons. 
Rénard. 
The quartzites of the Cambrian system are subordinate to the 
schists, “phyllades,” ete, so enormously developed in the lower 
beds, but the base of the Silurian is formed by a thick mass of 
whitish grit—the ‘Gres de Cabo Busto” previously mentioned—with 
its beds of “Grés a scolithes,” whose description strongly reminds 
one of the “annelid” or “pipe” rock of the N.W. Highlands, which 
is probably not far from"the same geological horizon. In the 
quartzites the author recognizes two principal varieties: the one is 
obviously clastic in its elements, though part of the mica may be 
endogenous; as regards the other, irregular fragments of quartz are 
enveloped in a subsequent deposit of the same mineral 
Some of the limestones, such as the COalcaire des canons, are 
characterized by many crystals of quartz similar to those described 
by Rénard as occurring in the Carboniferous Limestone of Belgium, 
and by Wardle, Clifton Ward, and others, in limestones of that age 
in England ; but which do not occur in the Devonian Limestone. The 
latter is also wanting in Foraminifera, their absence being explained 
by Dr. Barrois as owing to the changes which this porous coral 
limestone has undergone, and which have not affected the more solid 
rocks of the Carboniferous Limestone. The coccoliths of these beds 
are described as of inorganic origin, and their mode of formation 
explained (pp. 46-47) as resulting from the combination of organic 
matter with carbonate of lime. 
“ Roches crystallines massives.”’—The chapter on the massive crystal- 
line rocks completes the more especially lithological portion of the 
work, and is a valuable contribution to this interesting subject. Dr. 
Barrois has been doing for Galicia and the Asturias what Rosenbusch 
and many well-known authors have done for the Vosges and other 
classical districts, where similar phenomena have been studied. 
If anything is to be desired where all is so good, we may again 
remark that a few analyses, though less indispensable here than 
when treating of the phyllades, would have served to control the 
inferences derived from the microscope in the study of the granites, 
quartz-porphyries, diorites, diabases, and recent quartz-kersantites. 
There are two masses of eruptive granite posterior to the Cambrian 
schists: that of Boal has a length of only three kilométres on the 
surface, that of Lugo in Galicia is much more extensive. An absence of 
white mica is one of the features which distinguishes this larger mass 
of granite from the other, which latter would come under the heading 
“granulite” of Michel-Lévy. The contrast between the schists and 
the granites is most marked, nothing in the nature of a passage can 
be seen, nor do the schists ever contain a crystal of felspar. 
As regards their age, these granites penetrate the Archean rocks 
(couches strato-cristallines primitives), and the Cambrian schists, but 
the author has never found any reason for supposing that they are 
posterior to the Silurian, although certain elvans, which may be in 
