34 THE PHYSICAL FEATUEES OF PRINCE GEORGE's COUNTY 



1S09. 



GoDON^ SiLVAiN. Observations to serve for the mineralogical Map 



of the State of Maryland. (Read Nov. 6, 1809.) 



Trans. Amer. Phil. Soc, o. s. vol. vi, 1809, pp. 319-323. 



The author states that Washington is built on alluvial land and that Rock 

 Creek forms the boundary between the "primitive" and the "alluvial" strata, 



Latrobe^ B. H. An account of the Freestone Quarries on the 

 Potomac and Rappahannock rivers. (Read Feb. 10, 1807.) 

 Trans. Amer. Phil. Soc, o. s. vol. vi, 1809, pp. 283-293. 

 The course of the Potomac river below Washington is described. 



1817. 



Maceure, Wm. Observations on the Geology of the United States 

 of America, with some remarks on the effect produced on the nature 

 and fertility of soils b}^ the decomposition of the different classes of 

 rocks. 12mo, 2 plates, Phila., 1817. Is an elaboration of an article 

 published in 1809 in Trans. Amer. Phil. Soc, o. s. vol. vi, pp. 411- 

 428. Republished in Trans. Amer. Phil. Soc, n. s. vol. i, 1818, pp. 

 1-91. 



This work is classic, as it was the first attempt to treat the geology of the 

 entire country and contains the first published geological map of the United 

 States. The whole Coastal Plain constitutes the "alluvial" formation and the 

 Piedmont Plateau the "primitive." 



1818. 



Mitchell^ Samuel L. Essay on the Theory of the Earth by ]\T. 

 Cuvier to which are now added Observations on the Geology of Worth 

 America by Samuel L. ^Mitchell. 8vo, 431 pp., 8 plates. jSTew York, 

 1818. 



Describes the indurated shell rock at Upper Marlboro. Also describes the 

 topography in and about Washington. Mentions the finding of lignitized 

 branches and trunks of trees containing pyrite in abundance 54 feet beneath 

 the surface of Capitol Hill, and a "bough of sound and seasoned black wal- 

 nut" 45 feet below the surface near the Eastern branch. Bones and sharks' 

 teeth are reported from further down the river. "Digging has shown that all 

 the strata are horizontal; and the pebbles and stones mingled with the sand 

 are rounded as if worn by water," p. 396. 



