ELEMENTS IN SAND-PLAIN FORMATION 459 
greater velocity would have resulted, but not enough greater to 
have prevented the settling of the sediment. The ebb and flow 
of the tide, which is about four feet, would have decreased the 
outflow some 25 per cent. during flood tide, and increased it by 
a corresponding amount during the ebb. 
The average distance through which the water would move 
in its passage from the mouth of the glacial stream to the outlet 
would be at least a mile. The current, which at the frontal slope 
of the sand-plain had a velocity, as indicated by the material 
deposited, of some eight inches per second, would decrease until 
certainly not over three inches per second at the outlet. Its 
passage would require fully four hours. 
Sediment of glacial streams. — According to Helland,’ as quoted 
by Reid,? the maximum sediment values of their respective 
regions are represented by the Unteraar glacier of Switzerland, 
which carries .142 grams per liter; the Langedal glacier of Nor- 
way, Carrying .513 grams; and Alangordleck glacier of Green- 
land, carrying 2.37 grams. Both Wright and Reid found much 
more sediment in the waters from the Muir glacier of Alaska, 
the former recording a load which reduces to 12.12 grams per 
liter,3 and the latter a load as high as 12.98 grams per liter.t As 
the Alaskan glaciers most nearly represent the conditions 
obtaining during the closing stages of the continental ice sheet, 
I have taken Reid’s value of 13 grams (actual value, 12.98 
grams) as a basis in calculating the time of formation of the 
Barrington clays. 
In all probability the sediment discharged by the streams 
draining the continental ice sheet was even greater than that of 
the most heavily loaded glacial streams of today. I have sought 
to neutralize this difference as much as possible by applying as 
a mean value to the Barrington deposits the maximum value of 
the Muir glacier sediments. 
* HEIM’s Gletscherkunde, p. 363. 
? Sixteenth Annual Report, U. S. Geol. Surv., Pt. I, p. 457. 
3Ice Age in North America, p. 64. 
4 Loc. ctt., ps 454. 
