bascom.] MELAPHYRES AND AUGITE-PORPHYKITES. 71 
with shot. In other localities there is a greater diversity both in the 
shape and in the composition of the amygdules, 
There is frequently a zonal arrangement of three minerals — epidote, 
chlorite, and quartz — the light-green epidote being developed on the 
edge of the vesicle and surrounding the chlorite and quartz, which are 
successively developed in the interior Where the vesicles are large, 
epidote sometimes occurs in beautiful radiating crystals, not com- 
pletely filling the vesicle, and occasionally associated with crystallized 
malachite. 
It is doubtless to these amygdules that Professor Rogers refers when 
he describes the " decidedly crystalline" primal slates as containing 
"segregated specks and even half-formed geodes of epidote and other 
minerals," or "as gray slate spotted with epidote." Wherever there 
has been sufficient shearing to form a slate a micaceous mineral is formed 
in the vesicles. This micaceous mineral is either sericite, when the 
slate is conspicuously ornamented with greenish-white oval spots, or it 
is chlorite, when the slate is marked with brilliant dark-green oval 
spots. 
The nonamygdaloidal diabase is always more or less schistose and 
frequently slaty. At the second railroad cut beyond Gladhill's switch 
it has a banded appearance, due to an alternation in color, purplish green, 
dark and light green rapidly succeeding one another. The rock is fine- 
grained. The form of the banding and the structure of the rocks as 
disclosed by the microscope suggest that the bands represent ash beds. 
At the west end of the tunnel there is a curious differentiation of 
the diabase in color and sensitivity to pressure. This differentiation is 
limited to an irregular band which suggests in many ways an intrusive 
dike. The apparent dike traverses the nonamygdaloidal diabase in a 
direction oblique to the schistosity of the latter, At one end it diverges 
and sends out a branch which inirsues a course vertically downward 
and disappears beneath the surface. 
Fragments of the schistose diabase are included within the dike. 
Its upper surface is somewhat amygdaloid al, the interior compact, and 
the lower surface bordered by a band of light-yellow epidote. This 
band is more irregular in outline than the upper surface. 
The dike is intersected by two systems of line parallel, or approxi- 
mately parallel, quartz veins. Parallel to one of these systems is an 
easy cleavage. 
The diabase just above and below the dike is finely schistose. This 
schistosity is parallel to the course of the dike, and is particularly 
remarkable above the dike, where it follows every curve of the latter. 
The color of the dike is purplish, and contrasts with the surrounding 
dark-green diabase. 
The obliquity of this seeming dike to the general schistosity of the 
diabase, its inclusions of fragments of the surrounding schist, its 
divergent branches, and the foliation of the diabase parallel to the 
