326 FRA NK BURSLEY TA YL OR 



of miles, as is common in the West. Indeed, few if any have 

 been traced as far as ten miles. Nor has any method of corre- 

 lating the moraine fragments been worked out by which the 

 individual ice borders may be plausibly reconstructed across the 

 rugged country of New England. Because a distinct series of 

 recessional moraines has not thus far been found in the East, the 

 impression has prevailed in some minds that the ice-sheet may 

 not have had the oscillations and halts that it did in the West. 

 But this opinion has been held in spite of the suggestive 

 significance of the fragmentary evidences just mentioned. The 

 recent studies in Berkshire county have disclosed the fact that, 

 at least Within its boundaries, and in much of the country contigu- 

 ous to it, the recessional halts did take place with usual regular- 

 ity, and that fragmentary moraines were built along the several 

 lines on which the ice-front rested. It is more the object of the 

 present paper to show in particular what results bearing on the 

 manner of the retreat of the ice-front have been attained by these 

 studies. 



TOPOGRAPHY. 



The topography of Berkshire county is a rugged and varied 

 one. The development of the present relief and its drainage 

 systems has been almost entirely the work of subaerial agencies. 

 Rain and frost and streams like those now there have done the 

 work. Glacial erosion has been very slight. The develop- 

 ment of the relief has followed the distribution of the harder and 

 softer rocks, and lines of weakness in the former. The harder 

 members are the mountains and uplands of today, while the 

 valleys follow mainly the lines of the softer strata. The quart- 

 zite and gneiss of the Green mountain range, the various gneisses 

 of Hoosic mountain and the plateau to the south, the Berkshire 

 and Greylock schists of Greylock mountain, and the Berkshire 

 schist of Mount Washington and the Taconic range constitute 

 the principal areas of the harder rocks, and they are all areas of 

 high relief, while the Stockbridge limestone and a few other 

 less extensive, but relatively soft, strata lie chiefly in the valleys^ 

 and have determined their place and extent. 



Although the Berkshires are a mountainous region the 



