Page:Popular Science Monthly Volume 37.djvu/209

Rh and represents a deep but comparatively narrow cut in the underlying 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 construction 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 bowlders—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 destruction which such masses of rock are undergoing), between Groton and Noank, on the line of the New London and Providence Railroad, 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



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