70 W. W. Dodge—Menevian Argillites at Braintree, Mass. 
netic, sometimes pyritiferous. The fragments vary in size 
from a few inches in longest diameter, to many feet in length. 
Coarse syenite south of the Monatoquot slates holds inclusions 
of fine grained syenite. 
Penn’ ill 1s composed chiefly of the Quincy syemite, 
although based on the older eruptive. The principal area 
No modification in the Quincey syenite where it is in contact 
with the underlying syenite has been observed. The older 
rock may have been yet hot when the more recent covered it. 
No inclusions of the older in the newer have been identified. 
he great abundance of quart in conspicuous lumps in the 
upper rock makes it easily distinguishable from the older 
eruptive. On weathered surfaces the former is rough with 
these lumps, even when heavily lichened, the latter smooth and 
of a general yellow or brown color. The variety of the newer 
rock most quarried is blue, but the brown is also used. ; 
Mr. Wadsworth has published* the result of a microscopic 
examination of this syenite, both the typical form and the 
“bands” in it. One of these dikes (?), exposed at a quarry in 
Milton near the Quincy line, is five feet wide, with a direction 
H. 2° N., and inclination or dip to the northward, 25°. It 
meets the rock on each side with a distinct junction. It is 
intermediate tint. 
e rough woodland of western Quincy is much less favor- 
able for accurate examination of the distribution of the rocks, 
than the cleared, settled and carefully mapped parts of the 
town. The coarse syenite lies in great hill ranges, and the 
massive dark gray argillites lying upon the steep hill sides are 
much covered by fallen debris from the crests of the hills. 
The slates on the east side of Randolph Turnpike have a 
strike N. 70°-75° E., and are there exposed for a width of 
about ninety feet. 
Examination of the accompanying map shows that two 
slate bands pass under the Penn’s Hill syenite on its eastern 
border. The most that can be said as to the identity of the 
strata that appear from under these wide-s reading masses of 
eruptive rock at different points is that their similarity of char- 
* Proceedings of the Boston Society of Natural History, vol. xix, p. 309. 
