1()6 TI113 PHENOMENA OF DRIFT, OR 



many of thorn, is, that at least on one side, the surface has been 

 smoothed and striated. This may admit of explanation in two 

 ■^vays : — First, the atti'ition may have taken place before the 

 bowlder was raised from its original bed. Secondly, it may have 

 been produced while the bowlder was frozen into the bottom of 

 masses of ice, grating along a rocky bottom. The latter suppo- 

 sition corresponds best with another fact, not uncommon, namely, 

 that the edges of the bowlder, contiguous to the striated surface, 

 ai-e also rounded. The effect may, however, have been produced 

 sometimes in one way and sometimes in another. 



The size of some of our bowlders is very great. Those from 

 ten to fifteen feet in diameter are very common. Those from 

 twenty to twenty-five feet are less common. I have seen several, 

 as at Gay- Head and Bradford in Massachusetts, and in Win- 

 chester, in New Hampshire, fully thirty feet in diameter; and one 

 of conglomerate existed a few years ago, but is now a good deal 

 blasted away, at Fall River, in Massachusetts, which must have 

 weighed not less than fifty-four hundi'ed tons, or ten millions eight 

 hundred thousand pounds. I also recently measured one in An- 

 ti'im, in New Hampshue, whose horizontal circumference is one 

 hundred and fifty feet, and consequently its size must nearly equal 

 that at Fall River; although the vertical circumference in both 

 these bowlders is probably somewhat less than the horizontal. 



This country has now been examined with sufficient care, over 

 a breadth of longitude of more than two thousand miles, namely, 

 from Nova Scotia, through New England, New York, the Can- 

 adas, Ohio, Michigan, Illinois, and the region west of the lakes, 

 nearly to the Rocky Mountains, to make it certain, that the gen- 

 eral direction in which the bowlders have been carried is south- 

 easterly. The greatest part of the force by Avhich they have been 

 transported, has been confined between a south and southeast 

 direction. There are exceptions, indeed, to this statement, as in 

 the St. Lawrence valley and in western New York ; where the 

 course was considerably to the west of south. It is somewhat 

 so in limited spots in New England ; and on the west slope of a 

 hiU in Putney, Vermont, I noticed furrows running S. 35° W. 

 and N. 35° E. by the compass : that is, about 27° west of the 



