ESKAR EXCAVATION IN NOVA SCOTIA. PREST. 41 



fall of surface water at the first possible point of entrance 

 where the ice was thinnest. 



And now let us review as far as possible from the limited 



local evidence at hand the successive processes that brot 



about the present form of the Middlefield eskar. 



Review of At the bottom of the Middlefield crevasse, 



Evidence after the final pause of the ice sheet, began a 



slight erosion. This depression was afterwards 



filled in with modified drift. Its then stationary character is 



shown by the fine sediment that followed this erosion which 



was deposited among the exposed rocks of the boulder clay. 



This deposit is shown as No. 2 on the sectional 



Insufficiency plan. The conditions accompanying the de- 



theories position of this fine clay prevents the acceptance 



of any of the theories of origin usually applied. 



A glacial lake on the slope of this watershed is an impossibility. 



A super-glacial stream would have no source of debris supply. 



A subglacial stream on the top of a watershed could not 



wear and i3olish the eskar material at its very beginning as 



this was polished. None of these theories can explain all 



the peculiarities of eskars. 



A crevasse dammed by debris is the only explanation 



that will account for quiet water on the slope of a watershed, 



and its retention at such a high level. We find 



The only evidence here for the belief that each stage of 



solution erosion provided material for the damming of 



the crevasse and the beginning of a quiet water 



stage in which was deposited the finer material of the next 



beds. 



Beds No. 3, 4 and 5 show turbulent water conditions 



in a bed of smoothly worn boulders. The most striking 



peculiarity of these beds is that they show the 



A striking precipitation of mineral matter instead of clay. 



feature Beds No. 6, 7, 8, 9 and 10 make a series 



which show an increasing current to No. 7, and 



then a decreasing tho irregular current which ended in the 



extremely quiet water deposit at No. 10. The important 



