68 AN OUTLINE OF THE 



when the drainage lines had been for a long time under 

 control of sub-aerial streams, it is most probable that there 

 were no lakes on the Island in which the streams were 

 detained on their way to the sea ; now there are twelve 

 lakes, several of them of good size and most picturesquely 

 placed amid the mountains. If the land stood a little 

 higher, Somes Sound would be transformed into a lake, 

 for its waters are deeper in the line of the mountain range 

 than farther south at its Narrows. It is interesting to 

 notice that the streams which enter Denning Pond (Echo 

 Lake) and Great Pond come from the south, the head- 

 waters of the latter lying distinctly beyond the axis of the 

 range ; and that the northward outlets of these lakes lead 

 their waters into the head of Somes Sound, through which 

 they pass back again southward across the line of the 

 range to the sea. Such an arrangement of streams would 

 be unnatural or impossible in a region whose drainage 

 had been developed under the ordinary processes of at- 

 mospheric wasting; and must be, with the occurrence of 

 the lakes deep in the mountain axis, referred to glacial 

 action. It is noteworthy, however, that while the rock 

 scorings, the transported boulders, and the till are all 

 taken as demonstrating the existence of an ice sheet in 

 the recent past, the occurrence of the lakes and of the 

 reversed or northward drainage is not generally regarded 

 as belonging in the same demonstrative category. The 

 latter facts may be plausibly explained by the action of 

 the ice, the existence of which is to be otherwise demon- 

 strated, rather than regarded as independent indications 

 of ice action, even in the absence of other evidence. 



The altitude of the land at the time when the ice inva- 

 sion began is not known, except that for a considerable 

 preglacial time it must have been somewhat higher than 

 now, to allow the excavation as land valleys of the many 

 arms of the sea that now break up the coast line of Maine, 



