254 SOME EFFECTS OF ICE ACTION NEAR 



times the other was steeper, but for the most part they are 

 ahnost as much nlike as the two sides of a railway fill. 



Structure — Physically the material is of all sizes and 

 shapes from sand grains to boulders three and four feet in 

 diameter. .Asa rule it is gravelly, containing more stones than 

 the surrounding soil. There is no stratification, nor very 

 marked assortment of material. 



Mineralogically, the materials do not differ from those of 

 the adjacent soil. All the stones show a weathered surface. 

 Many are somewhat rounded, but this appears to be the result 

 of weathering rather than of water action. I found no facetted 

 surfaces, nor were there any glacial striae; the stones, how- 

 ever, were not of sufficiently close texture to receive or retain 

 such markings. A good deal of the "oil in the mound seems 

 to have resulted from the decay of boulders "in situ." 



Age. — On the mound are trees growing many feet in height. 

 One, which had recently been cut down, measured fifteen inches 

 across the butt, 2^ feet from the ground. The roots of this 

 tree, as of many others, spread out immediately at or below 

 the surface, indicating that it had grown on the mound after 

 it had been heaped up. This would show the deposit to be at 

 least as old as the tree. For a birch to grow to that size on 

 sterile soil and in a severe climate, would require 60 or 70 years 

 at least, probably more. 



From the weathering of the rocks contained, I would infer 

 A much greater age for the mound than that. 



Origin. — By the neighboring country folk, to whom these 

 mounds offer convenient, if somewhat erratic foot-paths, their 

 formation is readily explained. To the industrious beaver of 

 bygone days is given the credit of building these extensive ram- 

 parts. 



But the beaver, I believe, usually selects a spot on a stream 

 flowing through a narrow gap, to make his work as light as 

 nossible in proportion to the increase of depth in water thus 

 secured. These mounds, however, sometimes run through 



