SCIENTIFIC NEWS. 
143 
stone is more or less granular, and contains no organic remains, 
nor any beds of fetid limestone : when enclosed between beds 
of clay slate, it' is of a dark blue colour : when in contact with 
mica slate it is grey or white $ both varieties pass insensibly 
into the slate within which they are enclosed : and the lime- 
stone, the schistus, an - the sandstone, are evidently n. embers 
\ of one formation. 
The structure of Schehallien is the subject of the next ar- 
ticle. This mountain consists of a central ridge in vertical strata 
I flanked on every side by beds of mica slate nearly vertical, and 
containing subordinate beds of limestone. The rock composing 
this central ridge, though it has been denominated granite by 
some mineralogists of no mean name, is in fact the same as the 
granular quartz of Jura, being composed of highly compacted 
grains of quartz with interspersed grains of earthy felspar. The 
same quartz rock appears in the valley of the Lyon to the S. of 
Schehallien, and it seems that the mica slate alternates with 
beds of quartz rock ; and is, therefore, of the same sera as 
this latter. 
The vicinity of Criman, which is the subject of the next 
article, is remarkable for presenting nearly vertical beds of well 
characterized granwake and granwakke slate, with equally well 
characterized beds of clay slate and chlorite slate. 
The structure of the rocks bounding the vale of Abesfayle, 
is next described. On tracing this country up to Benledi alter- 
nations of granwakke and granwakke slate with clay slate first 
occur : then comes a fine roofing slate approaching in parts to 
mica slate, but distinguished by a true granwakke structure, that 
is of grains united by a slaty cement, only in this case the ce- 
ment is not clay slate but mica slate : beyond this, the true 
mica slate makes its appearance. 
The general deduction from these facts is, that those rocks 
which have been ranked as primitive schist alternate with rocks 
of recomposed materials, which belong to the transition class of 
Werner : but this alternation throws great doubt on the reality 
of transition rocks as distinguished from primitive, and rather 
tends to bring back the original division of rocks into primitive 
and secondary. 
ERRATA. 
