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BULLETIN OF THE LABORATORIES 
inch or two apart and which must have been subjected to the same 
agencies of metamorphism. One of these species presents all the 
characters of a typical granite with much quartz and orthoclase and few ac- 
cessories. There is some pyrite, probably secondary. The orthoclase 
is much altered and gives aggregate polarization. The quartz grains 
are filled with numerous fracture lines and are rendered almost cloudy 
with microlitic inclusions, both apparently the result of intense heat 
and pressure. The other variety is unmistakably porphyry, with an 
almost irresolvable ground mass of quartz filled with large crystals of 
orthoclase, with now and then a large grain of quartz. These pebbles 
also appear to be very much altered from the action of heat. The or- 
thoclase still can be determined by its aggregate polarization, crystal- 
line outline and perpendicular extinction. In microscopic characters 
this rocks resembles very closely the porphyritic phase of the schist 
further down the river. A mile or so above the falls is a shining, fis- 
sile chloride schist (No. 1027) which under the microscope proves to 
have a very uniform ground-mass of quartz and chlorite with a very 
little brown mica and numerous and regularly distributed minute un- 
terminated crystals of an orthorhombic mineral with optical characters 
of staurolite. Much of the schist is of a highly metamorphic charac- 
ter, but preserves the’ usual strike and dip. 
Nos. 1.016, 1029, T031, and 1036 are various phases of gneiss ex- 
tending from a point one-half a mile east of the union of Mountain 
river with Dog river, in the line of strike, to intersect the coast several 
miles northeast of the mouth of the latter. This series consists of 
several bands of varying width and texture interstratified and conform- 
able with the schists. No. 1016 occurs along the shore near the Terraces, 
forming high bluffs. It is a very fine-grained dark gneiss, with obvi- 
ous bands of flesh-colored feldspar. Microscopically the mass of the 
rock is composed of much green muscovite mica, considerable epi- 
dote in zones (recognized by its bright yellow color,) relatively large 
amounts of oligoclase and decomposing feldspathic ingredient (ortho- 
clase). There are innumerable needles of a transparent substance ap- 
parently derived from the mica. Some calcite is probably derived 
from the same source. Very little quartz is present. 
No. T036 is identical with No. 1016 and is from an adjacent ex- 
posure, but it is nearly schistose and the section exhibits a few veins 
