MARYLAND GEOLOGICAL SUEVEY 33 



and that tliej were transported to their present locations by glaciers 

 during late Jnrassic or earlj Cretaceous time. 



MeGee in 1886, speaks of the Pleistocene (Columbia) formation 

 in the Washington area as "appearing to represent a subaqueous 

 delta of the Potomac Kiver formed when the river was far al)ove its 

 present level." In 1887 he described the size of the boulders m the 

 Pleistocene deposits and stated that those brought down by the 

 Potomac River in Quaternary time were twenty times as large as 

 those now carried by the same stream. In other articles in 1888, 

 1889, 1891 and 1900 McGee further discussed these deposits and 

 gave excellent descriptions of their features in the Washington 

 region. 



Darton, in articles published in 1891, 1893 and 1901, made val- 

 uable contributions to our knowledge of these formations. In an 

 article published in 1901 Shattuck described the gravel deposits of 

 the !N"ortli Atlantic Coastal Plain, reviewed former ideas and classi- 

 fications of these late formations, and proposed the classification 

 adopted in this report. The latest and most complete discussion is 

 contained in a recent volume issued by the Maryland Geological 

 Survey in 1906 on the Pliocene and Pleistocene Formations of Mary- 

 land. It contains a full discussion of the deposits and also the fauna 

 and flora which they contain. 



BIBLIOGRAPHY. 



1621. 

 Smith, Johx. A Generall Historic of Virginia, Xew Englaml, 

 and the Summer Isles, etc. London, 1621. [Several editions.] 



This work contains many interesting notes on the physiography of Ches- 

 apealve Bay and its tributaries, and briefly describes the clays and gravels 

 along their shores. The "Powtomeke" (Potomac) river is said to be naviga- 

 ble 140 miles from its mouth. For a reproduction and discussion of Smith'^s 

 map see Md. Geol. Surv., vol. ii, pp. 347-360. 



