130 Scientific Geology, 



Dunes or Downs. 



Sand Is frequently thrown by the spray, or waves, during a storm, 

 so high upon the shore, that the reflux waves do not carry it back. 

 This being drie'd by the sun, is driven inwards by the sea breezes, 

 and in the course of time forms hills of conisderable elevation. Or 

 sometimes the wind from the sea raises the sand from a cliff of terti- 

 ary formation, and carries it inland. Thus are formed those moving 

 sand hills, which on the eastern continent, are called dunes or downs,, 

 and which have excited so much interest near the banks of the Nile. 

 As might be expected, these dunes are common along the shore in 

 the southeastern part of Massachusetts. They may be seen in the 

 greatest perfection and on the largest scale, on Cape Cod ; particu- 

 larly near its extremity. They are frequently as high as 60 or 70 

 feet, and on the east end of the Cape, they move towards the west, 

 but at what rate, in any instance, I was unable to ascertain. A series 

 of these dunes, several miles long, threatens the village and bay of 

 Provincetown, and large quantities of the beach grass have been 

 transplanted to their ridges for the purpose of arresting their progress. 

 I observed, also, that the two species of Hudsonia, which are com- 

 mon on the Cape, present no small obstacle to the advancement of 

 these sands ; though never transplanted, that I am aware of, for this 

 purpose. 



On both shores of Cape Cod throughout its whole extent, may be 

 seen dunes more or less extensive : and by their snowy whiteness 

 they sometimes give great interest to the landscape. I cannot learn 

 that any of them have been productive of such extensive mischief ta 

 farms and villages as has sometimes resulted from their progress on 

 the eastern continent. It would be strange, however, if the future 

 history of Cape Cod should not contain catastrophes of this kind. 

 Indeed, I have stated that they have aided in rilling up the harbor of 

 Chatham. 



Dunes of smaller extent, and of low elevation, occur on Nantucket,, 

 Martha's Vineyard, some of the Elizabeth Islands, and in many 

 places along the coast in the county of Plymouth. Moveable sand 

 hills also occur rarely in the interior of the state ; as, for instance, in 

 the Connecticut valley, in Montague, Hadley, and in Enfield, Ct 

 But concerning these I know of no facts of special interest, except 

 that they are slowly advancing towards the southeast ; indicating the 

 predominance of northwest winds. 



