PLATE 12. 
Figure 1.— Tinurtz Bzp In SLATE, Squantum Heap. 
About fifty feet above the tillite at Squantum Head, a bed of tillite occurs intercalated in the slate. 
At a point one and one fourth inches above the lower right hand corner. contact of this tillite with the 
banded slate is shown and one and one half inches above the lower left hand corner the upper contact. 
The average thickness of this bed is about four feet. The upper surface of the tillite is uneven as might 
be expected, and the lower surface, as far as visible, issomewhat uneven also. A large mass of slate is 
shown on the right. This slate mass was evidently ploughed out of its bed by advancing ice and included 
in the tillite. Other slate masses of smaller size may be seen to the left of the large fragment. Glaci- 
ated pebbles are visible, all through the tillite mass. Two of fair size are near the head of the hammer. 
The banding above and below the tillite has about the same interval between the bands. It is inferred 
from this that the water in front of the ice was of about the same depth before and after the advance, 
and that no glacial stream was very near this particular locality at the time. Further, it is inferred 
that this advance registers a small oscillation of the ice front and not an advance after an interglacial 
episode. Another similar bed of tillite, about twenty feet above the tillite and several beds of conglomer- 
ate, give evidence of the slow retreat of the main ice sheet. Just as the evidence at Woodsville, N. H. 
in the glacial clays, points to a very slow, lingering retreat of the Pleistocene ice, so these deposits at 
Squantum point to a similar slow retreat, marked by many oscillations of the ice front covering many 
years. 
Figure 2.— Fotpep SLaTn BETWEEN UNDISTURBED Layers, Squantum SOUTHEAST. 
About thirty feet above the tillite at Squantum Southeast, in bands of sandstone and slate, these 
beautifully folded layers occur. The folds are almost vertical but tilted slightly to the west. No 
pebbles have been observed in the folded zone. There is no cutting off of the folds on top, nor mashing 
as may be seen in the contorted zones at Squantum Head. As far as can be judged, by the evidence 
which this very limited exposure presents, the ice did not actually come in contact with the layers. The 
result observed is probably due to shearing, either by over-riding ice above this horizon, or by diastrophic 
movements while the beds were unconsolidated. It is also possible that creeping of the beds, induced 
by heavy superincumbent deposits, may have effected the result. 
