WIE WA SIE MHA S SINE, IROCTES, JE INC, 15 
ation of augite or of any other mineral now occurring in the 
rock. 
In those phases of the granulitic rocks that contain large 
quantities of biotite and hornblende, the former ntineral is often 
in large plates with irregular outlines and the cellular structure 
that has been referred to so frequently as characteristic of the 
constituents of these rocks. On its basal section the mica is 
reddish brown. Parallel to the cleavage it is almost opaque, 
while perpendicular thereto it is yellow. It includes grains of 
augite and is often includedin plagioclase. Most of the diallage 
in these rocks has disappeared and has been replaced by yel- 
lowish brown hornblende in grains of the same shape and size as 
the few augites remaining. In some sections that are otherwise 
quite fresh, individual augite grains are changed into hornblende 
often to half their extent. At some distance from their contact 
on either side of it the augite and the hornblende are well char- 
acterized. Near the contact their special peculiarities blend to 
form an intermediate substance that is neither a well defined 
pyroxene nor a typical amphibole. The structure of most of 
these varieties of the granulitic rocks is typically granulitic. 
There are a few cases, however, in which a departure from this 
structure- is noticed. In rock. No. 8000; for ‘instance, * the 
plagioclase grains are not all of nearly the same size. Large 
grains, with very ragged contours and small grains of the granu- 
litic character are both common in it. The former measure 
between .5 and 1.mm. in length and the latter rarely more than 
-Imm. No distinction as to age between the two feldspar can 
be made out. Sometimes the large grains seem to be younger 
than the small ones, and often they appear to be older. Both 
are more or less kaolinized and both include augite, hornblende, 
small colorless crystals and glassy particles. The other excep- 
tions to the characteristic granulitic type are no more striking 
than is this. 
Non-feldspatlic Varieties—The only granulitic rock free from 
plagioclase is No. 1334, which has already been referred to in 
another place (Vol) Il. p., 824); Dhis rock is’ more or less 
