SAYLES: THE SQUANTUM TILLITE. 159 
one hand that the slate masses are pebbles and on the other that they 
are pockets of slaty material laid down during the deposition of the 
conglomerate.” 
The slate masses referred to above are very similar to the slate 
lumps in the beds under the tillite at Atlantic. I consider their 
origin to be similar; disruption by moving ice and transportation by a 
glacial stream would explain it. No undoubted tillite has appeared 
north of Squantum Head and Roslindale, but clay fragments could 
have been transported by glacial streams beyond the ice-front for 
some distance. It is difficult to understand how clay particles could 
have been deposited in isolated pockets in so swift a stream as is 
indicated in this exposure by the size of the pebbles and boulders. 
Some of the boulders measure over a foot in diameter. 
Cleavage is found at this exposure. It does not appear that this 
rock is tillite. 
Locality 15. Waban. About half way between Eliot and Wa- 
ban railroad stations there is an outcrop on the south side of the 
track. The strike is N 38° E, and the dip 53°N., as determined from 
overlying slate. This rock is not tillite but has every appearance of 
-being on the tillite horizon. It is a very coarse conglomerate. The 
largest boulders are at least two feet in diameter, and are of angular, 
subangular, and rounded shapes. Melaphyre tuff appears to under- 
lie this conglomerate. Above the conglomerate are beds of sandstone 
transitional to a thick body of slate, which appears to be the Cam- 
bridge slate. This very coarse conglomerate may well be outwash 
material from the glacier. It is several miles west of the most westerly 
outcrop of tillite. 
Locality 16. Moon Island. At the most eastern extremity of 
Moon Island, which is, as a matter of fact, artificially connected with 
Squantum by a viaduct, there is an outcrop of the tillite. The 
strike is N 70° E, and the dip about vertical. The matrix is very fine 
suggesting the lower part of a tillite bed. There is no stratification 
and the included rock fragments are mostly angular, and subangular. 
No striated pebbles have been searched for. Some intercalated beds 
of sandstone and conglomerate may be seen. As this place was found 
very recently it does not appear on the locality map, and the criteria 
for tillite are not yet as complete as possible. Moon Island is a drum- 
lin, and at the tillite outcrop well-exposed till lies on the tillite. 
Criteria found:— A, B, C, D, J, K, L. 
Locality 17. Huit’s Cove. At Huit’s Cove, Hingham, on the east 
shore of Weymouth Back River, there is an exposure of the very top 
