— 
33 
sal of Mr. Benton's paper. The chlorite of the amygdules is 
quite different from the so-called viridite of the diabases. With 
a low power and by ordinary light it appears like a continuous 
sheet of a light green micaceous mineral viewed perpendicularly 
to its cleavage; but with a power of 400 or 500 diameters, it 
is seen to be a compact mass of minute scales which is almost 
black between erossed nicols, but which polarizes faintly as the 
stage is revolved and shows at the same time that the individual 
foliae have a fan-shaped arrangement. It very likely represents 
the final stage of the viriditie alteration, and is presumably the 
same as the dark green compact chlorite which. occurs in masses 
of some size in the amygdules of the melaphyr at Drighton. 
Numerous other minerals of secondary origin are found in 
the cavities and crevices of the melaphyr; but as they occur 
only in minute quantities in the material at hand and usually 
without well defined crystallographic outlines, their correct de- 
termination is a matter of great difficulty, and in some cases 
would be impossible. For this reason and because they do not 
appear to have any important bearing upon the problems under 
consideration I have omitted mention of them in my descriptions. 
Fourth Melaphyr, Coastal Area. — This is a fine grained 
greenish rock, with few macroscopic constituents. ‘True amyg- 
dules are rarely abundant in the melaphyr of this area, but 
it is very commonly distinctly brecciated, considerable masses 
having a highly fragmental aspect. Under the microscope it 
is found to consist of the usual lath-shaped plagioclases with 
step-like ends imbedded in a grayish amorphous ground-mass 
and showing a marked fluidal arrangement. Much secondary 
epidote is present, occurring in scattered grains, in strings or 
veins and in aggregates filling the numerous small cavities re- 
sulting from the decomposition of some of the original constitu- 
ents of the rocks. There is also present a considerable amount 
of viridite, which results from the alteration of the augites, 
and is also derived in part from the ground-mass. This at 
times occupies the entire interspaces of the feldspars, and, act- 
9 
OCCAS. PAPERS B. S. N. H. IV. 3 
