REVIEWS 99 



some vertical sections show extensive folding, faulting, and foliation of 

 the ice strata. 



It is concluded that pressure has had a very important role in 

 determining variations in the course of the glaciers, surface forms on 

 the glaciers, especially hillock moraines, stratification, and local deforma- 

 tion of the ice, and in the erosion accomplished. 



R. C. M. 



The S quantum Tillite. By Robert W. Sayles. Bull, of the 

 Museum of Comparative Zoology, Harvard College, Vol. LVI, 

 No. 2, Geological series, Vol. X, 1914. Pp. 141-75, pis. 12. 



The origin of the Roxbury conglomerate has always been a matter 

 of doubt. It has been held by a number of geologists to be of glacial 

 origin, while yet others have favored its marine derivation. 



Robert W. Sayles in the present paper describes a bed of what appears 

 to be tillite in the Roxbury series of Boston and vicinity. The Squantum 

 tillite has a probable thickness of 600 feet and consists of sand, angular, 

 subangular, and rounded pebbles and bowlders, and irregular fragments 

 of slate. The size of the fragmental material varies from that of a sand 

 grain to large, angular blocks, one bowlder having been found which has 

 a length of 6 feet and a width of 1 foot. Practically all of the material is 

 less than a foot in diameter, with the greater proportion less than 6 inches. 

 All of these fragments are firmly cemented in a matrix of argillite. 

 There are also intercalated beds of slate and conglomerate. 



The criteria necessary for the recognition of tillite are enumerated 

 and their application has been made to seventeen outcrops of this appar- 

 ently glacial material. Mr. Sayles presents strong evidence in favor of 

 the glacial origin of the Squantum tillite. The illustrated bowlders and 

 pebbles have a subangular outline and also show fairly distinct striae. 

 A striated bedrock has not been found, but this may be due to the nature 

 of the underlying rocks, which are slates and sandstones. 



In one locality the contact with the tillite and underlying sandstone 

 was very ragged, the suggestion being made that the sand deposit, before 

 having been firmly cemented, had been disrupted by violent movements 

 of the ice. 



The supposition is made that the movement of the glacier was from 

 the southeast, and that as the advance took place into the Boston basin, 

 the recently deposited beds of sand and clay were torn up and the frag- 

 ments mingled with the debris of the glacier. The intercalated beds of 

 slate, which become more numerous toward the top of the tillite, are 



