Editorial Comment. 3^7 
become darker in color, yet nearer the granite, and are still 
found to contain intercalated with them and with layers of lime- 
stone, bands of amphibolytes, which have a harder and more 
granitic look than the pyroxene gneisses, but are otherwise 
quite similar in appearance. They are somewhat more sharp- 
ly defined from the marbles than are the pyroxene gneisses, the 
transition from one to the other being often quite abrupt. The 
whole series is cut by dikes, veins or stringers of the granite 
which anastomose through it in a remarkable way. and the 
resulting appearance is most complicated. Nearer still to the 
invading mass these bands become more and more broken and 
indefinite, the number and size of the granite dikes increase; 
and at last comes the state of affairs where the dark rocks 
occur as inclusions in the granite. . In the southwestern portion 
of the large central batholith shown in the accompanying map, 
these inclusions are very numerous indeed. They vary in size 
from a few square inches to hundreds of yards, and have an ap- 
pearance very similar to the rocks of the bands at the border, 
looking, however, still a little harder. Farther and farther 
away from the contact they lose much of their angular form 
and appear simply as dark elongated streaks in the granite, 
which seems to be dissolving or absorbing them." (pp. 5"^)- 
The author describes in detail the microscopic characters 
of several thin sections with view to discover by comparison 
the source of the derived rocks. 
The foliated and banded red granite (1273) which is 
supposed to be the intrusive that has metamorphosed the lime- 
stones, has a structure parallel with that of the adjoining lime- 
stone. It consists of the elements usual in granite, quartz. 
oligoclase, mircrocline, orthoclase and biotite. It also em- 
braces muscovite. magnetite, pyrite, zircon and apatite. It is 
granular and allotriomorphic. 
The gray gneiss ( 12O8) is very quartzose, granular in struc- 
ture, approaching mosaic, and does not greatly differ from the 
last, embracing the same minerals, though the feldspar here is 
andesine in place of oligoclase. This gray gneiss is in patches 
in the red. 
A quartz dioryte gneiss (1271) is without distinct foliation, 
fine-grained, granular and light reddish gray. The orthoclase 
in this rock is so scant that it receives the name dioryte, though 
