EUROPEAN DRUMLINS AND MORAINES. 27 



of years held a nearly stationary position. According to the supposition 

 that two inches of daily summer ablation was approximately equaled 

 by the glacial onflow, whenever the ablation was at a faster average rate, 

 as three or four inches daily, the ice receded, depositing the smoother 

 till sheets between the hilly marginal moraine belts. 



During the stages of ice accumulation, up to the maximum of the gla- 

 ciation and to the lowan stage, I think that the ice-sheet eroded much 

 drift on its central area and bore it forward in the basal quarter or third 

 of the whole thickness of the ice, depositing much of it, however, as sub- 

 glacial till within fifty miles, more or less, back from its front. When 

 the final recession of the ice carried its border gradually backward over 

 all its area, I believe that the process of subglacial drift deposition con- 

 tinued, forming the ground moraine or lower part of the till progressively 

 as the ice border withdrew, and now and again, under exceptional climatic 

 conditions, amassing much of this till in drumlins. The part of the drift 

 which had remained englacial, when the frontal line in its retreat reached 

 the place of a temporary pause, permitting a marginal moraine to be 

 formed, was then borne forward in the manner described to the boundary. 



Only with a rate of ablation much faster and with glacial currents 

 much stronger than those of the Arctic regions or of the continental ice- 

 sheets during their time of accumulation under the severe climate of 

 their high plateau elevation, in short, only during the Champlain epoch, 

 when the land had sunk from its preglacial and Glacial altitude, both in 

 America and Europe, could noteworthy drumlins and peripheral mo- 

 raines be amassed. They record on each continent the definite closing 

 epoch of the Glacial period. 



European Drumlins and Moraines. 



We owe the earliest observations and descriptions of drumlins to Kina- 

 han and Close, in Ireland, and to Shaler, in Massachusetts. These re- 

 markable hills of till are admirably developed in portions of Ireland, 

 Scotland, and northern England. To what extent they exist on the gla- 

 ciated areas of northern Germany, Russia, and Scandinavia, appears not 

 yet to be clearly ascertained. 



During nearly forty years, from the first announcement by Agassiz of 

 his theory that the general drift-sheets of Europe and North America 

 were produced by vast sheets of land ice, their marginal moraines re- 

 mained unrecognized. Their true character was first made known some- 

 what less than twenty years ago by Clarence King on the Elizabeth 

 islands of southeastern Massachusetts, Chamberlin in Wisconsin, Lewis 

 and Wright in Pennsylvania, Cook and Smock in New Jersey, and the 

 present writer on Long island, Marthas Vineyard, Nantucket, and cape 

 Cod. After the grand development of these moraines of the North Amer- 



