Prof. T. G. Bonney—Quarts-Schists from the Alps. 205: 
the calc-mica-schist group is obviously folded up in a very com- 
plicated fashion between the underlying gneissose rocks.' The 
gigantic undulations rise and fall for thousands of feet. It is no 
exaggeration to say that an active climber in a single day might 
touch the schists at points separated by a mile vertical. I know of 
outcrops on the same path which differ in elevation by full 3000 feet.? 
But to describe in detail either these folds or the varieties of the- 
calc-mica-schists* would occupy too much space; on the present 
occasion I must restrict myself to the quartz-schists. 
This is a rock macroscopically very well characterized. It is a 
compact white quartz-rock,* containing a variable quantity of silvery 
mica, which is sometimes grey coloured. The latter mineral not 
seldom is almost absent from bands an inch or so thick; then it may 
become abundant, forming sometimes a layer hardly thicker than a 
sheet of letter paper, sometimes distinct bands in thickness, running 
up to about half an inch (seldom reaching one inch), when the rock, 
strictly speaking, consists of alternating layers of white quartz-schist 
and lead-grey or greenish-grey mica-schist. In weathering it shows 
a marked tendency to break up into slabs. This, for instance, is very 
conspicuous in the quartz-schists which crop out on the craggy slopes 
west of the hotels at Saas-Fee. The talus below is strewn with 
slabs about as thick as the tiles used in flooring an outhouse. The 
laminz of mica determine their separation, so that the surface sparkles: 
with little scattered flakes of this mineral, and the thicker blocks 
may be further split up with the hammer. The basset edges of 
the rock can be recognized at once by their peculiar “ flagey ” aspect 
and sharp, almost rectangular, jointing. In this section, as usual, 
the quartz-schist is associated with varieties of the calc-mica-schist, 
in which the mica is generally subordinated as much as in the quartz- 
schist. The change from the one rock to the other is rapid, but the 
cale-schist is often more micaceous in the immediate vicinity of the 
quartz-schist. The former becomes in places an almost pure marble ; 
sometimes also it is quite “slaty,” fine-grained, crumbling, and of 
a bluish-grey colour, at first sight very like some of the Mesozoic 
limestones of the Alps. The resemblance is the result of pressure ; ° 
the real difference becomes apparent on careful examination. 
The general relations of these schists are readily determined, but 
some minor questions are by no means easy to settle. It is quite 
clear that the mass, as a whole, is infolded between moderately coarse 
rather micaceous gneiss, of a type common in the district. The 
latter, often considerably crushed, may be seen cropping out in 
places both below and above, extending in the latter direction right 
1 Tt was my intention to give some particulars of these gneisses, but they would 
make the article too long, so I reserve them for a future communication. | 
* Between Saas-Fee and Saas im-Grund and on the peak of the Mittaghorn. 
° Many details are given in the papers to which reference has already been made. 
4 T avoid the term quartzite for reasons which will presently appear. 
° Other instances may be found both in this district and elsewhere in the Alps. 
The effect of pressure in crystalline limestones is discussed in this Macazinz, 1889, 
p- 483. 
