Dodge.] 
212 
[May 18. 
southerly dip is also exhibited in some of the ledges on the north 
bank of the river. The northerly dip, 45° to 60°, occurs in other 
ledges in the low ground north of the river. The rise of land 
south of River Street marks the change of the strata to pudding- 
stone. This rock occurs along the railroad west of Central Avenue. 
On the southern side of the axis, puddingstone forms a high mass 
on each side of the river near the chocolate mills east of the bridge. 
That on the south side of the river passes into slaty strata with a 
dip of about 68° near the railroad bridge over the river. The 
sandstone and conglomerate follow south of the track along the 
river as far as coal sheds on the west side, and on the east side 
these rocks, alternating, continue to a distance of 500 yards from 
the railroad bridge. 
At Cedar Grove Cemetery the sandstone and puddingstone out- 
crop are abundant. Here, too, the strike is H. 48° E. — S. 48° 
W., as shown by a band of sandstone between layers of the coarse 
rock in the ledges south of the lane which gives exit on Granite 
Street. The rock exposures extend east of this last named street. 
There is an anticlinal at the north-eastern point of Squantum 
formed by the sandstone and puddingstone beds, and easily seen 
at the shore. Southward, the strata dip southerly. The Dor- 
chester Bay tunnel makes it evident that the northern side of the 
arch has not been faulted away. 
The tunnel, which is for the reception of the Moon Island 
sewer, as is known, runs from the Calf Pasture south-easterly to a 
point on Squantum a little inside the Head. Its length is about 
6100 feet between east and west shafts. The channel is midway 
between the west and middle shafts. The rock sinks rapidly from 
the point under the channel to a depth of more than 100 feet at 
the west shaft, while between the middle and east shafts it rises 
nearly, and off the line of the tunnel, quite to the level of low 
water. 
Along the slope downward from the Squantum shore, pudding- 
stone was encountered, I am informed, above low water level, then 
“ red slate ” with quartz ; further down, more conglomerate. The 
rock was removed parallel to its natural bedding, that is, the dip is 
northward. Westward from the east shaft was “ red slate ” much 
broken up and with wide fissures. Intrusive rock was found 300 
