1894.] 217 IWoodworth. 
other boulders in the glaciated district, l)y settling from overlying 
ice. To the same conclusion — that eskers were arched over by 
ice — I am driven by the previously-described false esker near 
Hyde Park. If this dej)osit of till were made in an open-air 
stream, running water would readily have surmounted the debris 
and at least its upper portion Avould exhibit traces of erosion or 
deposition. 
Further than these remarks, it is beyond the ]>rovince of the 
writer to attempt, at the present time, a classification of eskers. 
Theories. 
Of the theories to account for tyi)ical eskers those which do 
not recognize the origin of the deposits within the field occui^ied 
by the vanishing ice-sheet need not for obvious reasons at this 
time of writing be discussed. American and Scandinavian geol- 
ogists are in essential agreement as to the deposition of eskers 
somewhere in the ice, views differing mainly as to the precise 
level in the ice-sheet. 
Messrs. G. H. Stone^, G. F. Wright'^ and G. 11. Barton^ think 
a superglacial origin presents the least difficulty. Russell* com- 
pares an esker with the deposit made in the tunnel of St. Lucia 
River in Alaska. Mr. Upham favors the ice-caiion view. 
Mr. Upham's theory of the formation of eskers is as follows^ : — 
Darinj? the Cliamplain epoch, as the time of disappearance of the last 
ice-sheet has been named by Dana, its superficial melting was rapid 
throughout the warm portion of each year, while the subglacial melting 
went on at a very slow rate through both winter and summer, the same as 
it had been during the entire epoch of glaciation. Owing to the rapidity 
of the melting on the ice surface, and to the amount of englacial drift 
thus exposed and subjected to erosion and transportation, we believe 
that the subglacial stream courses already existing were inadequate for 
1 On kames or eskers of Maine. Proc. Amer. assoc. adv. sci., v. 29, p. 510-519, 1880. 
Professor Stone has recently argued for the subglacial origin of the same eskers.— Jour, 
geol., Chicago, v. 1, p. 246-254, 1893. 
•i Op. cit. 
3 Verbally communicated tome. 
4 Amer. geol., v. 12, p. 232, 1893. 
* Amer. geol., v. 8, p. 381, 1891. 
