162 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
On Blue Hill Avenue opposite Hazelton Street, just north of Walk- 
hill Street, there is an outcrop of slate and an unstratified conglomeratic 
mass resembling tillite. Other doubtful deposits are as follows: — 
On railroad between Wollaston and Quincy. 
Black’s Creek, one fourth mile west of railroad. 
North Quincy, one half mile northeast of Atlantic station. 
Between Florence St. and Hyde Park Avenue, near Mt. Hope 
station. 
CLEAVAGE. 
As noted in the description given of the tillite, evidence of intense 
shearing is found in every locality. The cleavage dips, as a rule, 
in a northeasterly direction. The shearing is beautifully shown in 
some of the pebbles from the tillite, which have been split in two and 
the parts turned as if on a pivot. In a boulderet found at Squan- 
tum Head one half has been sheared from the other about one third 
of an inch at one end, while at the other end only slight displace- 
ment has been effected. Some of the pebbles have been indented, 
and others flattened and stretched. A great many have a puck- 
ered or wrinkled appearance suggesting flow-effects. Striations due 
to diastrophic movements may be found frequently and are en- 
tirely different from the glacial striae. Almost all the surfaces of 
the rock fragments in the tillite have been thus affected in some 
manner. With all the shearing, and other diastrophic movements 
which the pebbles in the tillite have been through it is not to be won- 
dered at that glacially striated pebbles and boulders are rarely found. 
Occasionally one of the surfaces of a pebble has been so placed in the 
matrix of the tillite as to escape the violent diastrophic movements. 
Some of the tillite exposures have been weathered and it is nearly 
useless to look for striae in these. At Hyde Park where Dr. La Forge 
found the best striated pebble yet brought to light, the rock has been 
freshly blasted and there is more hope of a successful search. ‘There 
is also an advantage here in a search for striations, in that the bottom 
of the tillite is exposed. As mentioned above, till contains finer 
materials and more striated pebbles at the bottom than at the top 
(Stone, 1899, p. 29-30). Wherever the bottom of the tillite has been 
found the matrix is much finer than in the places where the top is 
exposed. The difficulties experienced in extricating pebbles from 
the fresh matrix of the bottom of the tillite has been very great. 
Most of those taken out have been broken in many fragments. All 
of the striated pebbles but one were found near the bottom of the 
