THE HORIZON OF DRUMLIN, OSAR AND KAME 

 FORMATION. 



In an article in the first number of this journal on the nature 

 of the englacial drift of the Mississippi basin, I endeavored to 

 show by evidence drawn from a wide area of the mterior that 

 erratics dislodged from the summits of the hills of crystalline 

 rock in the northern region by the Pleistocene ice-sheet were 

 borne south within the ice in such a way as to be kept separate 

 from the basal material throughout the whole course of their 

 transportation, and that they were at length let down upon the 

 surface of the basal drift at the margin of the ice as a separate 

 deposit. The evidence seemed to force the view that the basal 

 material was not carried upward by transverse ice currents even 

 into the heart of the glacier much less to its surface. The facts 

 there cited seemed to make it clear that there is not only a 

 theoretical but a practical horizon of demarcation between the 

 englacial drift and the basal drift, and that under circumstances 

 of this kind — and they seem to have wide prevalence — there is 

 little or no confusion of the two. Very possibly this conclusion 

 does not hold equally good in very hilly or mountainous regions. 

 In carrying out into further application this distinction, it 

 seems well to specify the precise sense in which the term engla- 

 cial is used. It may be applied to any erratic material that, at 

 any time during its transportation, may be enclosed within the 

 ice even though it be essentially at the bottom of the glacier 

 and may have been actually at the bottom a little before and 

 may again be at the base a little later on ; or it may be applied, 

 less technically but more significantly, to that only which is 

 embedded in the heart of the ice and borne passively along with 

 it free from basal influences until it is at length brought out to 

 the surface of the terminal slope by the agency of ablation. 



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