194 M. L. FULLER 



such as would be required for the upbuilding of extensive plains 

 like those of the Stoughton Bay area, a base-level was reached. In 

 crossing a valley the roof of the tunnel would be at least as high as 

 the median height of the valley walls on the up-stream and down- 

 stream sides. The motion of the water would be mainly super- 

 ficial, and the lower or slack- water portion of the tunnel in the valley 

 or depression would become filled to grade with deposits, which 

 would eventually be left as an immense esker. No deposits of such 

 a character occur in connection with the plains in this region. 



In case of the plains of the Stoughton Bay area, there can be no 

 doubt that the streams supplying the material were englacial or 

 superglacial. Of the two, superglacial streams are the more prob- 

 able. It is clear that there was a connection across the ice between 

 the Stoughton and East Sharon plains, while the waters from both 

 flowed a short distance over the ice in their passage through the 

 Rattlesnake Hill outlet. If superglacial drainage existed at one 

 point, it is likely to have existed at several, and, in the absence 

 of all evidences of subglacial drainage, can reasonably be accepted 

 as the predominant type. It is not assumed that subglacial drain- 

 age was not common in other regions, nor that it did not exist to 

 some extent in the region now under discussion; but it played little 

 or no part in the upbuilding of the plains. 



Inception of lakelets. — In an earlier paragraph it has been pointed 

 out that there is every reason to believe that the ice had become 

 stagnant before the first of the lakelets of the Stoughton Bay area 

 came into existence, and it is probable that all movement had ceased 

 while the entire surface of the region was still covered by the ice. As 

 the melting of this stagnant ice-field went on, the hilltops began to 

 appear, and the superglacial drainage was obliged to seek the notches 

 for outlets. Seemingly, the first pass to be uncovered was the one 

 immediately west of Rattlesnake Hill, at an altitude of approximately 

 325 feet; but it appears to have been so situated that it was not 

 available to any of the superglacial streams, for an examination of 

 the ground shows that there was no outflow of water through this 

 pass. Following this, the next to be laid bare as the melting pro- 

 gressed must have been the notch immediately east of Rattlesnake 

 Hifl, at an altitude of 250 feet. This is the outlet which is known as 

 the Rattlesnake Hill outlet. 



