Diluvium. 



145 



In Truro, near the extremity of Cape Cod, the magnitude of these el- 

 evations and depressions is truly astonishing. One finds himself in a 

 hilly and even mountainous country; the elevations being often from 

 200 to 300 feet high, and very numerous ; and yet these are most obvi- 

 ously diluvial hills and valleys; that is, they are as obviously the result 

 of currents of water, as those inequalities of surface, of exactly the same 

 shape, which we find in the dry bed of a river. The fact is, this Cape, 

 below Orleans, consists almost entirely of coarse sand, which is more 

 easily piled up and scooped out than gravel ; and this, explains the 

 striking features of the diluvium in the region of Truro, which is 

 well worth a journey thither to examine. But one has only to look 

 at a map of Massachusetts, to see that the idea of these effects having 

 resulted from the action of any existing stream, is absurd ; since no 

 current of water, deserving the name of a river, can exist on that 

 part of the Cape : whereas the Missisippi, or St. Lawrence, pouring 

 tlown a mountain gorge upon a sandy plain, would be scarcely ade- 

 quate to produce the effects here witnessed. And as to this being the 

 result of the retiring or returning wave, when the strata were first 

 elevated, I shall take occasion to show, before concluding this sec- 

 tion, that the opinion is improbable. 



The same idea, of a force vastly greater than any now in action in 

 the State, having been exerted in the production of our diluvium, 

 forces itself upon the attention in many other places besides Truro. 

 All the eastern part of the State presents evidence of having been 

 swept over by a prodigiously strong current of water. Nantucket, 

 Dukes County, and tbe Elizabeth Islands, are almost entirely covered 

 with a vast quantity of bowlders, gravel, and sand, most of which 

 must have come from the continent. On Nantucket, bowlders and 

 gravel are rare ; only four or five large blocks occurring on the is- 

 land ; although those two or three feet in diameter are not unfre- 

 quently met with : and these, consisting of granite, gneiss, and quartz, 

 were obviously transported from the continent. On the Vineyard, 

 the bowlders are very numerous, and some of them very large ; and 

 although some of them unquestionably proceded from the mainland, 

 yet in one or two places, as in Chilmark, I strongly suspect the exis- 

 tence of granite ledges a few feet below the surface, from the quan- 

 tity and size of the bowlders : and yet one often sees very large 

 blocks in the diluvial covering of the clay cliffs, as for instance at 

 Gay Head ; where one or two of them that have rolled down to the 

 base, are from 20 to 30 feet in diameter. The Elizabeth Islands are 

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