F. G. Clapj? — Clay of Probable Cretaceous Age. 185 



the surface. Some of these fragments are as much as half an 

 inch in diameter. Mr. B. F. Smith, a prominent well driller 

 of Boston, reports a number of wells in the city, in which 

 peculiar soft white deposits were found directly underneath 

 the till. The material is said to cave badly and sometimes 

 contains much water. 



To Professor Crosby, who has made extensive investigations 

 regarding the borings of Boston, belongs the credit of being 

 the first to suggest the pre-Pleistocene age of this clay. Pro- 

 fessor Crosby writes as follows :* 



"We may profitably note the fact that some of the borings 

 reporting bed-rock in the section of Boston south and east of 

 Beacon Hill have clearly not reached any of the hard and 

 thoroughly solid rocks (slate, conglomerate, trap, etc.) such as 

 make up the whole of the bed-rock surface wherever it is 

 exposed in ledges and shallow excavations; but instead the 

 drill has passed from the glacial drift to imperfectly consoli- 

 dated sands, clays, marls, etc., in part of colors unknown to 

 the drift, and probably representing Tertiary strata underlying 

 the drift and filling deep depressions and valleys in the harder 

 formations or true bed-rocks of the region. The artesian well 

 of N. Ward & Co., on Spectacle Island, 560 feet deep, passed 

 through at least 360 feet of unconsolidated material, only part 

 of which could be regarded as glacial drift'; and the deep well 

 at the corner of High and Purchase streets in Boston, reported 

 as reaching the bottom of the drift at about 100 feet, is in 

 soft materials comparable with the Tertiary deposits of Mar- 

 tha's Vineyard and Long Island, to a depth of at least 500 

 feet." 



Conclusions. — Samples of the white clay from the Ames 

 Building boring were compared at the office of the United 

 States Geological Survey with samples of clay collected by 

 Mr. Veatch from a number of borings on Long Island, New 

 York, and found to agree very closely with them in appear- 

 ance. Mr. Yeatch has correlated the Long Island deposits 

 with the Raritan formation of New Jersey. f If this correla- 

 tion is correct, it is possible that the Boston deposits may be 

 of similar age. This is rendered more probable by the simi- 

 larity of the material in the Boston borings to some of the 

 clays on Martha's Vineyard, and by the fact that the beds on 

 that island referred to by Professor Crosby as " Tertiary " are 

 said by paleontologists to be in part of Cretaceous age. 



Previous most northern known Cretaceous and Tertiary. — 

 Cretaceous and Tertiary deposits have been known for years 



* W. O. Crosby, "Report of the Committee on Charles River Dam, Boston, 

 1903, p. 354. 



f A. C. Veatch, Outlines of the Geology of Long Island, Prof. Paper, U. S. 

 Geol. Survey, No. 44, 1906, pp. 22 et seq. 



