Chautauqua Grape Belt. 151 



by the action of tlie glacier. Over tliis coiuitry the glacier ice 

 slowly advanced until practically the whole of JMew York was cov- 

 ered, and for a time tliis ice sheet ground its way over the rocks, 

 carrying fragments southward and wearing down the valleys and 

 the hills as it passed. All life was of course exterminated from the 

 region and the land was transformed to a dreary icy plateau like 

 that of central Greenland. Why it came or how long it remained 

 are questions which the geologists of the future must answer, if we 

 ever learn. That it came and worked, performing certain tasks we 

 of the present century have determined. 



At last, by some change in the condition of the climate, the ice 

 sheet began to melt away and to uncover the buried land. It seems 

 to have done this quite rapidly, though somewhat intermittently. 

 That is, it would stand for awhile with its front along a certain 

 line, then quite rapidly melt away and transfer its front to a dis- 

 tance of a dozen or so miles to the north, where it would again take 

 a stand. This is indicated by the moraines, which are irregular 

 hills of glacial deposits that were accunnilated at the front of the 

 ice. The glacier was carrying a load of rock materials, and when 

 these reached the front they were dropped from the melting ice 

 and therefore accumulated. If the ice stood long enough a moraine 

 was built along the margin ; if its stand was brief no morainic 

 accumulations were made. One of these moraines passes through 

 Jamestown, another past the northern end of Lakes Chautauqua, 

 Bear and Cassadaga, and in a general east and west line back of the 

 crest of the escarpment. Another line passes just east of Silver 

 Creek, one near Hamburg, and another through Crittenden. 



Beneath and in the ice was a load of rock fragments wliich w^ore 

 moving southward. They were being ground over one another and 

 over the bed rock, so that they were being reduced to clay by the 

 scoui-ing action of the ice, which w^orked somewhat like a great 

 sandpaper. When the glacier disappeared, this material was left 

 where it happened to be, and so a soil was deposited which was 

 composed of clay and pebbles derived from various sources to the 

 north. This till or boulder clay was dragged into many of the old 

 valleys, either wholly or partially filling them, so that the streams 

 have often been obliged to cut new channels in the shale. Some- 

 times these rock gorges end abruptly where the stream crosses or 



