144 Scientific Geology. 



they must have been in this case, if they came from the region of 

 Scituate and Cohasset, 40 or 50 miles ; and that too, through a re- 

 gion of sand. And although much of the granite of these bowlders 

 resembles that of Cohasset and Scituate, yet I doubt whether it is 

 identical with it. Some of it I know to be quite different. 



The sand, which is the predominent ingredient of the diluvium in 

 the counties above named, was undoubtedly derived from a tertiary 

 formation, which has been broken up by diluvial action. Remnants of 

 this formation are occasionally seen on Cape Cod ; and in Truro, so 

 lofty and distinct are the cliffs of clay, that they have been noted on 

 the map. Clay is found in other places on the Cape ; but not in 

 large quantities, and generally at a low level. On Martha's Vine- 

 yard and Nantucket, this formation is much more abundant and ob- 

 vious along the coast ; though covered for the most part in the inte- 

 rior with diluvium several feet thick. Very likely this formation 

 once occupied no small part of Massachusetts Bay, and probably also 

 Buzzard's Bay. 



In almost every part of the State the diluvium is piled up into ele- 

 vations whose surfaces exhibit curves of every description ; while the 

 correspondent cavities are of various shapes. These convexities and 

 concavities resemble very much the sandy or gravelly bottom of ex- 

 isting streams, where the current has been very violent ; except that 

 generally those in 'the diluvium are on a vastly larger scale. The 

 sketch below may aid in imparting a correct idea of these diluvial 

 irregularities. It was taken in the southeast part of Amherst, and 

 exhibits several elevations from 10 to 20 feet high, composed entirely 

 of gravel, with no blocks large enough to be called bowlders. 



Diluvial Elevations and Depressions : Amherst. 



