BEACH AND COVE GRAVELS. 



45 



make clear its origin. At first it appeared to be till, but it was soon seen . 

 to have lost the finest matter of the till. All material except the finest 

 remained in a rather obscurely stratified condition On the northern slopes 

 of the island the stones have been changed but very little from their till 

 shapes; but on the side next the open ocean the stones are much more 

 rounded and polished, though seldom showing such very round shapes as 

 those of the stones of the present beach. A section from east to west across 

 one of the north -and-south valleys of the island is shown in the accompany- 

 ing diagram. 



The slopes are somewhat exaggerated in the diagram. The bare 

 ledges on the tops of the hills have become weathered into bowlders of 

 decomposition. Some of these are in place; others have tumbled or slid a 

 short distance down the slopes, as is proved by their identity in composition 

 with the rocks that compose 

 the ledges. Are these bowl- 

 ders the result of a former 

 marine erosion? The lower 

 part of the valley is shown 

 in fig. 6 to be filled by a 

 mass which we now recog- 

 nize as beach gravel, com- 

 posed of the till and any 

 rock which may have been eroded or washed up by the surf This is 

 ovei'lain by a thin soil composed of peat and vegetable mold, rain wash, 

 weathered drift, etc. An examination of the till and the beach gravels at 

 high levels showed that both are composed almost wholly of rocks found 

 on the mainland to the north of the island. I did not succeed in find- 

 ins: a single fragment of the same kind of rock as that on the island. The 

 beach gravel is evidently the residue left after the erosion of the far-traveled 

 till brought hither from the north by the ice. The finest matter of the till 

 was washed out to sea and lost, but the coarser matter remains, and con- 

 sists of sand and gravel mixed with larger stones and bowlders, all more 

 or less polished and rounded by water. The rarity, perhaps total absence, 

 of local rock in this ancient beach is a proof that the sea did not form 

 cliffs of beach erosion in the solid rock, though it was able to remove large 

 areas of till. It also justifies the inference that, at least in all the cases 



Fm. 6.— Trausv 



nt cove gravels. 



