SAYLES: THE SQUANTUM TILLITE. 161 



This will explain why some of the descriptions give so few glacial 

 characters, and does not mean that such an outcrop would not reveal 

 many more glacial characters if opportunity were granted to hammer 

 and blast. 



In spite of the small outcrops and those which I have not been able 

 to investigate properly, the average percentage of criteria for all 

 localities so far as the present investigation has gone, is slightly over 

 61%. Taking the first five of the localities given in the list, and the 

 percentage of criteria is 80%. The best locality of all, Squantum 

 Head, gives a percentage of 93%. A further search for striated 

 pebbles by the blasting method would probably raise these percentages 

 materially. So far nothing but geological hammers and chisels have 

 been used. The striated rock-floor or pavement is entirely wanting. 

 There is no prospect of finding- this on account of the nature of the 

 beds underlying the tillite. 



In view of the sum total of the evidence found in these different 

 localities, I am forced to the opinion that there is true tillite in the 

 Boston Basin. No other theory explains the evidence so far brought 

 to light. 



Doubtful localities. 



About 500 feet northwest of Canterbury Street on Morton Street 

 southeast of Forest Hills Cemetery, there is a conglomerate outcrop. 



In an open field 300 yards south of Walkhill Street and one fourth 

 of a mile southeast of Harvard Street there is an outcrop of slate, 

 sandstone, and perhaps tillite. 



