130 CONTRIBUTIONS TO THE GEOLOGY OF MAINE. [bull. 16? 
cement of similar materials. The fragments are at times 3 inches ii 
the longest diameter, and the larger siliceous fragments -bow agate an( 
structures. 
The medium-grained varieties pass into sandstones and are light greq 
in color and marked by many small, black slate fragments of some 
what larger size than the general mass, but otherwise the rock is o: 
very uniform texture. There occurs a variation from this medium- 
grained type, in which the angular grains are quite widely separatee 
by an unusual amount of finer-grained cement and in which occasional 
disks of slates an inch or more in diameter are found. On weathered 
surfaces these three varieties -how the siliceous fragments projecting 
above the more readily dissolved cement, and their extreme angularity 
is thereby well displayed. Fossils are sparingly found in all these 
rock-. 
A fine-grained variety is dark bluish gray on fresh fractures, and 
weathers white gray along- zonal lines, which are quite distinctly 
marked. No grains in this are large enough to be distinguished with 
the unaided eye, except the ever-present black -late fragment-. One 
variety is so dense, indurated, and tine textured that it resembles 
io*neous rock- of felsitic character and its nature is only revealed bv 
the microscope. 
J/' des ' .—Several slides were prepared from the 
different varieties which showed dose similarity in all point- excepi 
size of grain. The medium-grained variety was taken as^ typical and 
was found to contain quartz and feldspar, with some accessory materials] 
in addition to the fragment- of volcanic rock, which are the most abun- 
dant of all the components. The quartz is in broken, cracked, angular 
and -ubano-ular grains — none round — about one millimeter in longest 
diameter. Feldspar includes both orthociase and oligoclase, the latter 
with bright lamellae. The lava fragments are rhyolite, trachyte, and 
andesite, with the first two more abundant and with flow structures 
Sedimentary material i- represented by a few fragment- of arkose and 
slate. Zircon grains are sparingly present. The cement i- 1 »f tine mate- 
rial, identical in composition with the larger fragments, but altered to a 
yellow micaceous substance. Another variety i- so largely composed 
of andesitic fragments as to deserve the name of andesitic tuff. The 
dense, indurated variety mentioned above is found to be made up of 
quartz grains and fragments of siliceous lava-. In all the variety - of 
volcanic conglomerates from New Sweden, so far a- examined, micro- 
scopic fragment- of brachiopods and other fossils were found. 
VOLCANIC CONGLOMERATES OF PEEHAM TOWNSHIP. 
The volcanic conglomerate^ of Perham Township present a dark 
bluish-gray variety, in which the components are not megascopically 
di-cernible. and a light-gray variety of medium grain, occasionally con- 
