RIVER alluvions; 



'fiapitol hill and the Potowmack, including the shores 

 of Goose creek, and the tract along Pennsylvania 

 avenue, tov/ards the elevation on which the Presi- 

 dent's house stands, may be considered as having 

 been covered by water, and brought by the action of 

 that fluid to its present form. G radually, however, 

 as the channel deepened, the water withdrew to its 

 bed, narrowed its course, and left the intervening 

 surface bare. 



Asa proof of this, it is observed tliat all the strata 

 of earth hereabout are horizontal, and ail th-e stones 

 •and pebbles they consist of are rounded, and appear 

 to be water worn. This is the case every where on 

 the eastern branch of the Potowraack, and the parts 

 of the city which have been dug away for the pur- 

 pose of making streets, avenues, and buildings. 



But the most remarkable fact is, that even the 

 base of the Capitol hill is underlaid with a stratum 

 of muddy clay, in which wood and parts of trees have 

 been discovered. During the summer of 1803 a well 

 "was dug in New Jersey avenue, to the depth of near 

 fifty feet. After passing throu^^h about tliirty feet of 

 .gravel and sand, and through about eighteen feet of 

 ■dusty and fine argillaceous mud, trunks and branches 

 of trees were found lying plentifully below. Many 

 pieces of these were broken and hoisted up. 



Their vegetable organization is very evident ; and 

 their clefts and crevices are filled up with veins of 

 pyrites. The wood, as commonly happens when 

 :inixed or impregnated with pyrites^ is turned to a 

 blackish colour, somewhat resembling coal. .But th^s 

 carbonated state of the woodj being evidently caused 



