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W. W. Dodge—Menevian Argillites at Braintree, Mass. 65 
ART. V.—On the Relations of the Menevian Argillites and 
associated Rocks at Braintree and vicinity, in Massachusetts ; 
by W. W. Dover.—With a map. 
THE well known syenite of Quincy, Massachusetts, occu- 
pies an area a mile and three quarters wide with its northern 
and southern sides running approximately east and west,—a 
little north of east, and south of west. It forms two principal 
cast-westerly lines of steep sided hills, or ridges cut across by 
glaciation. From the base of these, the rock extends to some 
distance on the more level ground. From Quincy, the rock 
extends into Milton on the west, and a short distance into 
Braintree on the south. 
€ northern of the two lines of hills ends near the Old 
Colony Railroad on the east, but in the southern there is a de- 
tached eminence, known as Penn’s Hill, east of the railroad. 
This hill is separated from those to the westward by a valley 
half a mile broad, in which the local rock, whatever its char- 
acter, is concealed by stratified gravel and sand there formin 
4 plain about forty feet above high tide, in which the railroa 
runs, and through which Town River flows from Braintree to 
ts outlet east of Quincy (Center) village. 
Some of the several hills may represent independent out- 
Branch Railroad and Washington Street (the road from Quincy 
to North Weymouth and Hingham), in Quincy and Braintree, 
the most abundant surface rock is a fine-grained syenite, which 
underlies the coarse Quincy syenite, and is entirely distinct 
Tom it. The fact that the two are not merely varieties of the 
Same rock seems to have been overlooked. For the purposes 
of the following account of the two eruptives, the older will 
be called the Braintree syenite. 
he expanse of the older rock is interrupted by bands of 
SS ge in which at one point occur Paradomides and other 
Ossils, 
_ Stratified Rocks (S on the accompanying map.)—Concern- 
ing the stratified deposits at the south shore of Boston Harbor, 
only such details need be here presented as seem to have sig- 
nificance concerning the relations of the strata and their dispo- 
Sition with reference to older and newer rocks. 
Of the stratified rocks in an anticlinal fold bordering on the 
north the coarser syenite in Quincy, the sandstones and slates 
©n the north side of the narrow conglomerate axis measure, 
AM. Jour. Sc1.—Tarp Sertss, Vor. XXV, No. 145.—Janvary, 1883. 
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