802 SoLLAS — A 3fap to shotv the Distribution of Eskers in Ireland. 



Mr. W. O. Crosby* writes of eskers as formed by sub- and super-glacial streams ; 

 but subsequently speaks of superglacial rivers alone. Thus he says: — "The 

 glacial streams had undoubtedly, in many cases, deeply grooved and divided the 

 marginal portion of the ice, and in these grooves or channels was accumulated, 

 after the manner of rivers, the narrow deposits of sand and gravel, which, when 

 the ice melted away, became the steep winding ridges which we call kames and 

 eskers. At the mouths of these glacial rivers, delta-plains were formed in the 

 lakes, adjacent deltas often becoming confluent. The plains are thus naturally 

 coincident in height with the eskers and often appear as expansions of the latter." 

 The subglacial origin of eskers is again asserted by Mr. Stone, f in an interesting, 

 but highly theoretical, Paper, in which he calls attention to the fact that, in the 

 State of Maine, along 200 miles of coast, the eskers decrease in size as they proceed 

 towards the sea ; at the same time becoming increasingly discontinuous, until they 

 terminate near the heads of fjords, without extending beneath the sea. Mr. Stone 

 thinks an explanation may be found in the glacial submergence, which prevented 

 the subglacial tunnels in that part of the ice which entered the sea from enlarging 

 with the same rapidity that they did elsewhere ; the result being that the sub- 

 glacial rivers, being confined within narrower channels, flowed with such velocity 

 that detritus was swept away and deposition rendered impossible. J 



Mr. Stone's Paper is followed by a very important contribution from Professor 

 Chamberlin,§ who shows that drumlins are essentially of subglacial origin, and 

 that kames are associated with them in such a manner as to prove that the gravel 

 of the kames "is but a partially assorted derivative from the till of the region." 

 A somewhat similar result is reached in the case of eskers. 



A very instructive model showing the relations of sand-plains, eskers, and kames 

 to each other, and to the stagnant glacier which is supposed to have produced them, 

 are described by Mr. F. P. Grulliver.|| 



A suggestive Paper, by Mr. J. B. Woodworth,5[ appeared in 1894. In discussing 

 the variation of the crest-line of eskers in height above the surrounding country, 

 the author suggests that this may be connected with changes in the breadth of the 



* Geology of the Boston Basin, by "W. 0. Crosby : Occasional Papers of the Boston Soc. Nat. Hist. IV., 

 vol. i., pp. 160 and 274, 1893 and 1894. 



f The Osar Gravels of the Coast of Maine, by George H. Stone : Joum. Geology, Chicago, vol. i., 

 p. 246, 1893. 



I A review of this Paper appeared in the American Geologist, vol. xii., p. 122, criticising some of its 

 conclusions. A reply by Mr. Stone follows in tlie same volume, p. 200. 



§ The Horizon of Dnwilin, Osar and Kame Formation, by T. C. Chamherlin : Joum. Geology, Chicago, 

 vol. i., p. 255, 1893. 



II Joum. Geology, Chicago, vol. i., p. 803, 1893. 



^ Some Typical Eskers of Southern New England, by J. B. Woodworth. — Proc. Boston Soc. Nat. 

 Hist., vol. xxvL, 1894, p. 197, 



