380 ON THE NATURE AND ORIGIN OF 



to the passes before the eskers were deposited, or the hills 

 bare of ice". Here Mr. Stone comes perilously near the 

 true theory of esker formation, whi ch he makes more probable 

 on page 363. Here he says: ''The fact that we find a gravel 

 ridge without a delta in a place so favorable for the formation 

 of a delta indicates that the ridge was deposited within ice 

 walls before the ridge had retired as far north as the esker". 



Subglacial Streams. — He presents evidence that calls for 

 a totally different theory of origin and yet>efuses to grasp 

 it, for on page 426 he says: "For the subglacial waters to 

 flow transversely to the motion of the ice must have been 

 the exception rather than the rule". 



Indefinite Theories. — This uncertainty is voiced by many 

 authors, who, after considering the evidence for the different 

 theories, have been unable to come to any decision. One 

 investigator says: "It might happen that the same esker 

 river was in different parts of its course, subglacial, englacial 

 and superglacial". Another hopeless sentence is: "So com- 

 plex is the problem that it cannot be claimed that all the 

 elements have been set forth". 



Thus there is little hope of a satisfactory^ solution to the 

 mystery of the origin of eskers among such indefinite theories. 



Such appears to be the general opinion of our foremost 

 geologists, among whom are Chamberlain and Salisbury. 

 Their Geology, Vol. VIII, is also a review, and indefinite 

 conclusions abound in it. 



Tremendous Velocity of Subglacial Streams. — Speaking of 

 eskers they say: "Subglacial streams seem sometimes to 

 have deposited gravel and sand in their channels". With 

 commendable caution they say: "It is not to be inferred that 

 eskers never originated in other ways, but it seems clear 

 that this is one method and perhaps the principal one by. 

 which they came into existence". And again: "Long eskers 

 sometimes wind up and down over low elevations and valleys^ 



