EVIDENCES OF GLACIAL ACTION IN CONNECTICUT. 197 



and represents a deep but comparatively narrow cut in the under- 

 lying hard granitic rocks ; and which, certainly near its mouth, 

 to a depth of fifty feet or more beneath. the present river-bottom, 

 as was shown by the recent borings in connection with the con- 

 struction of the Shore Line Railroad Bridge at New London, is 

 now filled up with mud or coarser detritus. East of the mouth 

 of the Thames River the shores of the mainland, and the surface 

 of the numerous little adjoining islands, are strewed with bowl- 

 ders — many of large size, and often resting on a highly smoothed 

 basis of bed-rock without the intervention of any surface soil 

 whatever; as is illustrated by Fig. 1, which represents (from a 

 photograph) a bowlder (and the changes in the way of destruc- 

 tion which such masses of rock are undergoing), between Groton 

 and Noank, on the line of the New London and Providence Rail- 

 road, and which is a very conspicuous object as seen from the 

 cars, on the left hand side of the track going east.* 



The number and size of the bowlders that are strewed over the 

 bottom of Fisher's Island Sound are also a matter of interest and 



Vza. 2. 



wonderment to even those least acquainted with the subject, who 

 sail over and fish in its shallow waters ; while Fisher's Island 

 itself is little other than a mass of bowlders covered in great 

 part by sand, and probably marks the terminal line where a 

 heavy ocean surf arrested the further progress of the glacier by 



* All the illustrations accompanying this paper are reproduced from photographic 

 pictures. 



