110 The American Geologist. August, 1S95.. 
tal line would reciiiire an average forward current of 26 inches 
daily for the lowest 400 feet of the ice-sheet. On the land 
bed, where it was impeded by friction, the rate was very small, 
thence gradually increasing upward. In the second mile the 
ice would retain its hight unchanged untler this ablation by 
an average ontlow of 4.,S feet daily for the stratum of ice 200 
fest thick terminating in that mile; the third mile would re- 
quire for its stratum of 150 feet a daily current of 5.8 feet ; 
and the fourth and tifth miles would require currents, respec- 
tively of 7.3 and S.8 feet. Between nine and ten miles from 
the ice front, at an altitude of 1,257 to 1,.312 feet, the ablation 
could be offset only by a current of 16 feet daily. By such 
currents, urged forward by the great weight of the more cen- 
tral and increasingly thicker part of the ice-sheet, the super- 
ficial wasting of the ice border would be evenly balanced, ^ 
holding, therefore, the nearly steady frontal line indispensa- 
ble for abundant marginal drift deposition. The gradients 
thus assumed for the ice surface near its boundary are proba- 
bly twice as steep as they were during the earlier stages of 
predominant ice accumulation. Hence, with the greatly in- 
creased Champlain temperature, the rates of glacial move- 
ment were perhaps five or even ten times faster than during the 
maximum stage of glaciation. 
If the outermost five miles of the ice, having the conditions 
here assumed, remained in essentially unchanged position 
thirty years, the total volume of drift there becoming super- 
glacial would be equivalent to about 50 feet on a width of one 
mile. With the previously superglacial drift of the same oviter 
belt of the ice, which, like the foregoing, must have been car- 
ried forward to the boundary, there would be a thickness of 
about 85 feet; and with all received in the same time from the 
more distant part of the ice surface, up to ten miles from the 
margin, the total terminal mass of drift would equal at least 
an average of 100 feet on a belt one mile wide. This amount,, 
amassed by the small frontal oscillations of the ice so as to 
form irregularly grouped hills and ridges, separated, as those 
of the moraines usually are, by deep and wide hollows, would 
constitute a morainic belt probably unsurpassed either in 
North America or Europe. Under the same conditions, a 
small but distinct moraine might be formed in only five ov- 
