182 ROCHESTER ACADEMY OF SCIENCE. 



etc., as shown in the courses of existing eskers. The absence or 

 poor development of eskers on divides and on steep downslopes is 

 due to the greater velocity of the subglacial streams in those situa- 

 tions. Yet velocity on downslopes was not excessive, we have here 

 to deal with something analogous to a tube of flow. Hence some 

 deposition may have taken place on downslopes, the water not pos- 

 sessing sufficient velocity to carry the heavier material and exces- 

 sive load to the front of the ice. Further, streams with sharpest 

 gradient did not develop the highest esker ridges. The low ridges as 

 well as the ridges having low, lateral slopes have the higher gradient 

 as a rule (7). On long gentle slopes and across plains the eskers 

 have their strongest development. 



Courses transverse to the direction of ice movement may be 

 accounted for by the formation of eskers after ice movement had 

 ceased, or by assuming a change in the direction of ice flow near the 

 closing stage of the ice epoch, the movement being in the general 

 direction of the esker trend and not being recorded on the till coated 

 surface beneath the ice, or by the stream maintaining its course 

 against the ice flow. This theory accounts for the tendency of the 

 esker ridge to bend in the direction of ice movement as when cross- 

 ing a valley in which the motion of the ice was obviously down the 

 valley axis (7). 



Eskers are also strongly developed beyond localities where the 

 ice had crossed easily eroded rocks, thus getting a large basal load 

 to be contributed to the subglacial waters. 



This method of origin accounts for the character of the strati- 

 fication, its chaotic arrangement of layers, its cross-bedding, the 

 tendency to dip toward the terminus of the eskers, the anticlinal 

 structure due to sliding and slipping of the beds as the restraining 

 ice walls on either hand were removed. "Pell-mell" structure may 

 be explained by the excessive slipping and irregular sliding of the 

 materials coming to rest, by ice push subsequent to the formation 

 of the esker (102), or by collapse of the subglacial tunnel in which 

 the esker ridge was deposited (40). Variations in supply of water 

 from day to day, and from season to season would account for many 

 modifications in bedding (40). 



This theory also accounts satisfactorily for the character of the 

 materials, their subangularity near the origin of many eskers when 



