170 CONTRIBUTIONS TO THE GEOLOGY OF MAINE. [bull. 165. 
pericline and Manebach laws also occur. The Carlsbad twins present 
are often with one half dropped much below the other, and all the 
twinning is more or less along irregular ragged lines and with unsym- 
metric development. None of the feldspars are entirely fresh, but 
are kaolinized along the cleavages and zonal boundaries, or are entirely 
altered to kaolin and calcite except upon their outer borders. They 
also show irregular cracks other than cleavage, along which strain has 
been relieved. Glass inclusions, arranged without order, are numer- 
ous and stand out prominently in the clearer parts of the feldspars. 
Orthoclase was not found outside the groundmass, except as forming 
the wide outer rim of the zonally built plagioclases. 
The pyroxenes are of both monoclinic and orthorhombic varieties. 
The monoclinic is an augite, light colored in thin section, with an 
average extinction on prism sections of 42°. The basal sections 
are quite fresh, and show the cleavage parallel to the prism. The 
pinacoids are more developed than the prism faces, and give the 
appearance of a square with truncated corners, rather than the more 
common octagonal effect. The prism sections vary from stout forms 
to those five or six times as long as broad. In places many small 
pieces are arranged in parallel position and separated by alteration 
products in such a way as to suggest the presence of augite pheno- 
crysts, of which these fragments are the remnants. The orthorhombic 
pyroxenes are represented in the darkest-colored rocks by a few basal 
and prism sections, but in the gray varieties it constitutes fully half 
of the pyroxenes present. It is very light colored, not at all pleo- 
chroic, is at times partly eaten away, and in other cases occurs as 
intergrowths parallel with the augite. It seems to be a variety poor 
in iron ; is optically -f- , and hence referred to enstatite. In the fresher 
rock specimens the cleavage cracks and borders of the enstatite often 
show the presence of a red-brown fibrous mineral. In the more 
weathered rocks this mineral assumes a prominent role. It is here 
found intergrown with augite and forming fibrous laths, with parallel 
extinction. Its pleochroism is distinct, with a= light brown, c= light 
green. The presence of this mineral in a slide seems to be in propor- 
tion to the absence of the orthorhombic pyroxene, and this, together 
with its shape and optical properties, points to bastite and makes 
plausible the supposition that the red-brown mineral is the present 
representative of the original orthorhombic pyroxene. The magnetite 
is present in grains or dust aggregates, and the apatite occurs in 
needles, laths, and rounded sections within the feldspars. 
The groundmass consists essentially of long, narrow feldspar laths, 
with ragged outline and split ends, arranged with trachytic structure 
tending toward the hyalopilitic, and with flow phenomena developed 
in places. No close distinction can be drawn between the groundmass 
feldspars and those which rise slightly above it, as all sizes, up to the 
