Reviews—Dr. Barrois’ Geology of Asturias, ete. 270 
Santander occupies one of these sheets, and affords a curious illustra- 
tion of the loops and folds into which the strata have been pressed. 
In connection with the subject of the general folding of the 
country, there is an instance—selected out of several—of a pair of 
synclinal folds of the Cambrian beds, which embrace within them 
the Scolithes-grit of the Silurians in such a way that, on one side, 
the relative positions are completely reversed, and the older becomes 
the upper rock. Such sections help to explain the causes which 
have been fruitful of much mystification in former times. Still the 
doctrine of pseudoclinal structure or the “oldest uppermost,” must be 
used with moderation and only on the clearest evidence, or it may 
lead to very serious results. 
The superficial extent of the Cambrian schists and “ phyllades” is 
very considerable, but the basal grits and quartzites of the Silurian 
form the prominent crests, and the naked and desolate ridges which 
have arrested the attention of the first observers. This Grés de Cabo 
Busto, or Scolithes-grit, has strong features of resemblance to the 
corresponding deposit in Brittany, whilst its orographical importance 
in other parts of Spain is very considerable. In the province of 
Toledo it rests directly on the crystalline primitive schists, without 
the interposition of the Cambrian “phyllades.” ‘Its position in the 
general stratigraphical column, as may be seen in the table, is 
between the beds of the primordial fauna with Paradoaides and the 
schists of the second fauna, and thus at present Dr. Barrois is satis- 
fied to place it at the base of the Silurian in Spain. 
The amount of calcareous beds in these lower formations is 
relatively small, but there is a great increase of limestone in the 
Devonian, and especially in the Carboniferous, corresponding to a 
great increase in fossils. The Calcaire des cantons, belonging to the 
latter system, gives rise to some remarkable scenery. 
Such is a brief outline of the stratigraphical position and general 
aspect of the sedimentary rocks, whose lithology is described in 
the first chapter (pp. 21-62), which is devoted to the mineral 
and microscopical characters of the ordinary argillaceous schists, 
“phyllades,” quartzites, and limestones of Paleozoic age in the 
Cantabrian mountains. 
As regards the schists no general relations can be detected between 
their lithological classification and their age (p. 20). The exogenous 
or clastic elements are quartz, felspar, and white mica, the endogenous 
ones being quartz, rutile, tourmaline, white mica, chlorite (p. 31): 
as a rule endogenous felspars are absent. In the Asturias schistosity 
corresponds generally with the stratification, and whilst molecular 
movements have given rise to spangles and needles of crystallization, 
the traces of organisms have not been destroyed. 
The author concludes that endogenous elements predominate in 
the composition of these schists. But, since rutile and tourmaline 
cannot form a very large percentage of the mass, we must suppose 
that what he identifies as ‘“‘ white mica” and “chlorite” are, in con- 
junction with quartz, the prevailing minerals. A little laboratory 
work at this point would have been, a very useful adjunct to 
