340 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 21, 



2. On the Tertiary and more recent Deposits in the Island of 

 Nantucket. By M. E. Desor and Edward C. Cabot. 

 (In a letter to Sir Charles Lyell, Pres. Geol. Soc.) 



Knowing how mnch you are interested in all inquiries about the 

 drift of this country, we take the liberty to forward to you some 

 specimens of shells which we have lately collected from the cliffs of 

 Sancati Head, in the island of Nantucket. Allow us to accompany 

 them with some observations upon this locality. 



The cliff of Sancati, as you know, constitutes the eastern border 

 of the island of Nantucket, rising to a height of ninety-two feet above 

 the beach. Although covered in a great measure with the loose sand 

 that is carried by the wind from the beach, yet there are several 

 points where the successive layers are to be seen, as for example near 

 the tripod : fig. 1 will give an idea of their superposition. 



•■r\>'.-/:'^.-:<y.\;':\''yy/.'^'i^^^ 



Fig. 



1. 









6 feet 



«. Dune sand. 





1 





d. Peat. 





37 





c. Sand with an occasional stra 





5 

 10 



)> 



turn of coarse gravel. 



d. Ferruginous gravel. 



e. Sand. 





2 





/. Worn shells. 





3 



1 



>) 



g. Serpula. 

 //. Ovsters. 





1 





i. Tough clav. • 





4 

 2 



>> 



y. Homogeneous white sand, 

 k. Gravel. 





20 



>) 



/. Brown clay. 



At the base of the cUff is found a stratum of brown, very brittle 

 and partly sandy clay (/), nearly twenty feet thick. Over this rests 

 a bed of gravel several feet thick (A), which is overlaid by a stratum 

 of homogeneous white sand (J). On this is found a layer of very 

 tough clay (z), very similar in its aspect to the plastic clay near Paris, 

 except that it contains a great many nodules of ferruginous sand. 

 This clay -bed is overlaid by an oyster-bank (/«) one foot thick, inter- 

 mixed and covered by large masses of Serpula ((/), which are, like the 

 oysters, in their natural position. There are besides a great many 

 other shells scattered through this bank, all of them in a most perfect 

 condition, although it is difficult to preserve them entire when taken 

 out from the layer. This oyster-bank is followed by another fossi- 

 liferous stratum (/), in which the shells are in a different state : they 

 bear evident traces of exposure, the valves of the bivalves being 



