540 Prof. T. G. Bonney—Serpentines from the Rhetian Alps. 
mass of dark-green serpentine. Here, also, the relations of the 
serpentine with the schist are almost inexplicable, except on a theory 
of intrusion—as may be seen on the (inaccessible) left bank of the 
stream. The macroscopic character of the serpentine is very similar 
to that of the rocks already mentioned. Microscopic examination 
shows it to be an altered olivine-enstatite rock, each mineral 
occurring in rather more distinct grains than usual, and, as we may 
infer from the greater abundance of opacite in both, rather richer 
in iron than in the other cases. The schist, in a gorge immediately 
above, is much contorted, and its surface is glaciated. Under the 
microscope it is seen to consist of grains of a yellowish epidote, flakes 
apparently of a clear mica, microlithic rods of an iron oxide, and a 
clear mineral, which is for the most part more probably felspar than 
quartz, all very minute. There is but little appearance of separation 
into distinct mineral layers, and the rock has not a very highly 
altered aspect; still I beliéve these minerals to be all of secondary 
formation. 
On approaching the village of Marmels, an extensive mass of 
serpentine is seen to occur in the hill-side on the right bank of the 
valley, and, at the entrance of the village, the road passes through 
a cutting. The rock here is an ophicalcite, rather schistose-looking, 
but really only a crushed serpentine, cemented by subsequent infil- 
tration. The principal mass of serpentine, judging from blocks by 
the road-side, is of the usual character. Some distance above the 
village this rock is crossed by the road. Here is also a considerable 
mass of gabbro. This varies from very coarse (diallage crystals up 
to nearly half-inch diameter) to rather fine, and it exhibits occasion- 
ally a slightly schistose structure—a character not rare near the 
exterior of gabbro masses. It can be seen by the road-side cutting 
through the serpentine. The last rock differs a little from those 
previously described, being an altered olivine-augite-enstatite rock. 
The first of these minerals is, as usual, changed into serpentine; the 
last is more or less serpentinized, but the second generally is in good 
preservation. There are two or three grains resembling enstatite in 
form, but wholly replaced by iron oxide.! 
Two specimens of the gabbro have been examined microscopically. 
One, of the coarser variety, was taken from a block, recently broken 
by blasting, in an old moraine a little lower down in the valley— 
but undoubtedly from some part of the mass (the specimens seen in 
sitw not being in good condition) ; the other, finer, was obtained 
from the mass which cuts through the serpentine. The former con- 
* The following analysis is given by Prof. Theobald of a serpentine from Marmels : 
8 
SiO, = 38°8 
Al, 03 = 4-67 
MgO = 36°41 
FeO. Fe,03 — S266 
20 = 11-37 
99-96 
As there is no CaO 
Biehaeane eet the analysis, probably the specimen did not contain augite, 
