1990] Mineralogy and Petrography. 139 
The peridotite contains hypersthene and amphibole, Its olivine is 
perfectly fresh, and is in irregular grains imbedded in the amphiboloids. 
Some of the granulites contain corroded crystals of bright red andalu- 
site, and also black tourmaline, sphene, muscovite, and garnet dissemi- 
nated in a ground-mass of feldspar and quartz. Other granulites are 
very rich in cordierite, and these are in general less rich in quartz than 
are those bearing andalusite. Micaceous and quartzitic schists from 
the neighborhood of Ax embrace zircon, apatite, sphene, magnetite, 
and numerous other materials, thought to be due to the action of the 
‘granulite on the schists. On the granulite side of the contact this 
rock is found to be charged with andalusite, and often with cordierite. 
Pyroxenites consist of a colorless diopside, zoisite, garnet, calcite, 
occasionally quartz, and frequently vesuvianite, of which latter it is 
possible to isolate beautiful amber-yellow crystals of the variety egeran. 
In the second article by the same author is a discussion of the changes 
effected in acid inclusions by the basaltic and acid rocks of Auvergne. 
Two classes of these inclusions are recognized, viz., those found in 
lava streams, and those occurring in volcanic necks. Both classes in- 
clude granites and gneisses rich in quartz, and frequently containing 
cordierite, sillimanite, garnet, corundum, diaspore, and zircon. The 
ges effected in them by the basic lavas varies in intensity, but not 
materially in kind. In extreme cases the inclusion has been entirely 
dissolved, with the exception of the insoluble substances, such as silli- 
Manite, zircon, and diaspore, which remain as grains in the volcanic 
glass. ‘The cleavages of the original feldspars have been accentuated, 
any liquid and gaseous inclosures have been developed in them, and 
the optical properties of the orthoclase have been changed. Quartz 
fragments in the altered forms have been surrounded by aureoles of 
| DA aa minerals developed in the surrounding rock by the 
i Ante = = Inclusion are spinel, hypersthene, and sometimes labra- 
: pee Sg forming holocrystalli. e aggregates, and at other 
aos : oe. as individual grains bathed in a vitreous paste. “In 
an ae case the minerals are met with only in the lava that has been 
: a oae tie components of the inclusions. They are not 
of the region are gneisses and kersantites. In most 
= i Sa the changes that have been produced in them are analogous to 
FER Produced by the basalts. Much new feldspar has been generated 
them a 
ii a: TER is usually optically continuous with the original feld- 
mo. is attached. ridymite is also an abundant new 
ae ‘ieee spinel and hypersthene. All these minerals are 
