Leverett — Observations on Craigton Lake. 433 



The slopes of the country are such that as the ice border 

 receded from south to north across this area, there were two 

 lines of discharge from it, one directly into Lake Fork valley 

 and the other into an eastern tributary leading past Big Prairie. 

 These two lines of discharge will be referred to as the Lake 

 Fork and the Big Prairie outlets. The position of the southern 

 end of Craigton Lake is such that the waters became ponded 

 in the immediate vicinity of Craigton before the ice had 

 receded from the highlands on the west far enough to allow 

 discharge past Funk into Lake Fork. As a result there was 

 drainage through the Big Prairie outlet down to the beginning 

 of Craigton Lake. By reference to the map it will be seen that 

 the summit in the bed of this outlet, at what may be con- 

 sidered its head, is about 1J miles south of Craigton and is 

 959 feet. There is a very slight fall for two or three miles 

 farther south, and this part of the outlet is included by Pro- 

 fessor Hubbard in the lake area ; but from Cnstaloga westward 

 there is a descent of nearly 40 feet in five miles to Lake Fork 

 valley. Professor Hubbard appears not to have recognized 

 the Big Prairie outlet, though the present drainage leads down 

 it from the summit above mentioned, 1-J miles south of 

 Craigton. Not having the help of a topographic map, and 

 because of the windings of this outlet between morainic ridges 

 and knolls, it is perhaps not surprising that he did not recog- 

 nize it. 



While this Big Prairie outlet was in operation the level of 

 the water near the head of the outlet appears to have been at 

 times as high as 967 or 968 feet, or eight or nine feet above 

 the bed of the channel, the evidence for this stage of the 

 water being found in sandy bars along the sides of the channel. 

 Near Cnstaloga, as noted by Professor Hubbard, the highest 

 water level seems to have been only about 960 feet. This 

 slight descent of seven or eight feet in the three miles from 

 Craigton to Custaloga being in the direction of the flow of 

 waters from the southern end of Craigton Lake, seems easily 

 accounted for without bringing in deformation or tilting. 

 Inasmuch as Professor Hubbard was ignorant of the southward 

 discharge through this outlet he accounted for the descent by 

 shore tilting. 



As soon as the ice border had receded past the north end of 

 the upland that lies between the two outlets the waters of 

 Craigton Lake were free to take the lower of the two outlets. 

 This, it may be inferred, was Lake Fork channel, from the 



The map also shows only such moraines and ice border features as have close 

 relation to the history of Craigton Lake. Inasmuch as Craigton Lake 

 and its outlets occupied what are now the major lines of drainage in nearly 

 the whole extent of this map, and since the contours come out more clearly 

 by omitting the drainage lines this has been done. 



