24 NEW YORK STATE MUSEUM 



slope facing the river. It is evident that it originally extended far- 

 ther to the east and has been cut away by river erosion. 



The interpretation placed upon the facts pertaining to the mo- 

 raine, above reported, is as follows : When, in the final retreat of 

 the lobe of ice occupying the central basin, the ice front stood in 

 the line of the present moraine, a halt or stationary phase in its 

 recession supervened. The causes which determined this may have 

 been general, that is, climatic, but it seems probable that local con- 

 ditions were at least contributory factors. The moraine lies in that 

 part of the depression where the mountainous highlands to the east 

 and west are at their greatest elevation. Between the present level 

 of the basin in its lowest part and the highest point of the eastern 

 highlands (Mount McGregor) there is a relief of 505 feet, while 

 the western highlands show a maximum relief of 1390 feet. These 

 figures indicate the greater thickness of the ice lying over the de- 

 pression as compared with the ice covering the uplands during the 

 period of general glaciation. As the rate of movement (flowage) 

 of glacier ice depends upon the pressure or " head " of the ice mass, 

 this thicker valley ice moved faster than the ice of the uplands. If 

 we suppose that, at the time of the melting of the ice, when the ice 

 front stood in the line of the present moraine, this differential mo- 

 tion of the valley ice had not been entirely dissipated — the per- 

 sistent mass of ice to the north still supplying " head " — it would 

 follow that the front of the valley ice lobe would become stationary 

 whenever the increment of advance became a deciding factor in 

 effecting a balance between the movement of the ice and the loss 

 by melting. 



Along the stationary front the earthy materials borne by the mov- 

 ing ice were released by the melting of the ice and deposited. 

 Through the accumulation of these deposits the moraine was built 

 up. While relatively stationary the edge of the ice advanced and 

 receded, within limits, thus spreading the deposits and forming a 

 belt of debris. The edge of the ice was irregular and the larger 

 protrusions, depositing their load along their margins, resulted in 

 the lobed form of the moraine. Through the detachment of mas- 

 sive fragments of ice and the heaping of debris about them, ice 

 block holes, or kettles, were formed. Variations in the amount of 

 materials brought to the edge of the ice at different times and at 

 different points and the control of the deposition of these mate- 

 rials by the irregularities of form and shiftings of position of the 

 edge produced the rounded hills and short ridges which are charac- 

 teristic surface features of the moraine. The streams issuing from 



