HOLMEs^J ANACOSTIA A'ALLEY QUARRY-SITES 71 



Many similar sites occur at corres]K)iuling localities on the other 

 branches of the Auacostia. There is little doubt that tlie iuhabitants 

 of Nacochtank resorted to tlie quarries of liock creek and Piny branch; 

 for great numbers of leaf-shape blades of quartzite, as well as of 

 quartz and rhyolite, are found on the chain of sites extending all the 

 way from Bennings to a jioint opposite Alexandria. 



THE TIDEWATER POTOMAC 



The Potomac formation, which yields the great body of workable 

 bowlders, exteiuls far down tlie river, but is found to yield smaller 

 amounts of available materials as the distance from Washington 

 increases. The outcrops are generally at considerable altitude above 

 the river, and at many points on the lower levels there are deposits of 

 bowlder-bearing material derived from the erosion of the Potomac beds. 

 This redistribution is now going on, so that everywhere there are more 

 or less extensive accumulations of workable bowlders. The superior 

 formations, the Lafayette and Columbia, also yield considerable work- 

 able stone, which is reassorted and redistributed l)y the river. There 

 are iu places de])osits of exceptionally hea\y bowlders of limited 

 extent as far down as the confluence with Chesapeake bay. About the 

 mouth of the Wicomico, for example, bowlders are found in large 

 numbers. On Popes creek and along Port Tobacco river the gravels 

 furnish many bowlders of all sizes, which were extensively used by the 

 shell-bank peo])les for mortars and nuillers, and for shaj)ing both small 

 and large implements. The valley of Zakiah creek, in Charles county, 

 is noted for the great number of arrowpoints and spearheads to be 

 found on its banks; while the gravels are well supplied with workable 

 pebbles of (juartz and (piartzitc, suitable for the implement maker. 



On the western side of the river, from Kosslyn to Potomac creek, 

 and extending far back into the hills, extensive deposits of bowlders 

 are exposed. In all of this district no quarries have been observed, 

 although it is probable that iu hundreds of places bowlders have been 

 obtained liy excavation ; but it would appear that the deposits outside 

 of the immediate vicinity of Washington were nowhere sufQciently 

 rich in workable material to encourage quarrying on a large scale. 

 Workshops are, however, found throughout this region, and refuse 

 coriesponding in every respect to that of the great quarries is widely 

 distributed. 



Especially notable sites are the high terraced points ab(_>ut jMount 

 Vernon and on the it^land of Chopawonisie, several miles below. From 

 the former Mr William Hunter has made extensive collections, n()w 

 for the most part owned by the National ^Museum, and it is not unusual 

 to see collections of quartzite and quartz points from the neighboring 

 fields ottered tor sale to visitors at Mount Vernon. At Chopawonisie 

 a bed of bowlders outcrops near the upper end of the island oidy a 

 few feet above low water. The debris of manufacture of quartz and 



