MAKYLAXD GEOLOGICAL SUEVEY 47 



1808. 



CoPE^ E. D. (On the discovery of the fresh-water origin of cer- 

 tain deposits of sand and clays in Avest ISTew Jersey.) 



Proc. Acad. Nat. Sci., Pliila., vol. xx, 1868, pp. 157-158. 



A brief concise description of the distribution and character of the de- 

 posits, now designated the Potomac Group, is given and Tyson is quoted as 

 believing that they are of Jurassic rather than Cretaceous. "The whole 

 formation indicates the existence of an extended body of fresh water, having 

 a direction and outline similar to that in which were deposited the red sand- 

 stones and shales of the Triassic belt, which extends parallel to its north- 

 west margin throughout the States in which it occurs." (p. 157.) 



1875. 

 JoiixsTOx, CiiRiSTOPirEE. About the Ttediscovery of the ''Ber- 

 muda Tripoli" near Xottingham, on the Patnxent, Prince George's 

 County, ]\rd. 

 Proc. Boston Soc. Nat. Hist., vol. xvii, 1875, pp. 127-129. 

 The writer describes the circumstances connected with the discovery that 

 the so-called "Bermuda tripoli" never came from Bermuda, but from the 

 vicinity of Nottingham, Prince George's county. 



SuLLivAKT, J. [Letter to Professor Christopher Johnston on Ber- 

 muda Tripoli in Maryland.] 



Proc. Boston Soc. Nat. Hist., vol. xvii, 1875, pp. 422-423. 



The writer expresses his belief that the so-called "Bermuda Tripoli" did 

 not come from Bermuda or Bermuda Hundreds, Virginia, but from Notting- 

 ham, Md. 



1870. 



Fontaine, W. M. Xotes on the Mesozoic of Virginia. 



Amer. Jour. Sci., 3d ser., vol. xvii, 1879, pp. 25-39, 151-157, 229-239. 



Brief descriptions are given of the iron ore clays of the Potomac group in 

 the belt extending from Washington to Baltimore. He speaks of the Potsdam 

 and Azoic boulders about Washington and between there and Baltimore 

 which he thinks were brought down during the Jurassic by icebergs and 

 glaciers. 



