34 



STONE IMPLEMENTS 



|ETH. ANN. 15 



beyond llie present city boundary, Florida avenue lU-rn we are 

 already i a tlie midst of tlic (|Uarrv-slioi) sites, ami the rudely worked 

 stones may l)e jjicked u[) on all sides. 



The quarries occur about half way uj) the wooded slo])es nortli and 

 south of the branch, on botli sidc^s of Fourteenth street, but tlie refuse 

 has descended to the stream beds and is found everywhere in the over- 

 placed gravels of the lower levels. The most extensive evidences of 

 ancient working occur on the northern side of the stream west of the 

 road. Here the terrace is upward of 100 feet in height and its faces 

 extremely steep. The map presented in plate ii serves to indicate the 

 distribution of quarries over an area of about half a mile square. The 

 bluffs at this point are capped with about 40 feet of the Potomac 

 formation, clays, sands, gravels, and bowlder beds, the Neocene deposits 

 of the Lafayette formation which forms the higher levels of the region 

 having disappeared from the outer promontories, or being but slightly 

 represented by obscure remnants. Beneath the Potomac beds the 

 gneisses are exposed (figures 1 and 2) and may be seen at several 



Fig. 3 — Panoramic view of Piny brancli quarry sites, looking north. The irregular dotted line indi- 

 cates position of the quarries and the crosses mark the principal points of study. 



points, especially about the bridge. They are more fully exposed 

 farther down toward Rock creek, into which the branch flows half a 

 mile below. The gneisses, as well as the Potomac beds resting on 

 them, disintegrate and crumble on and near the surface through the 

 action of various agencies, thus giving rather smooth though steep 

 slopes on which the forest maintains itself with much uniforunty. The 

 surfaces are usually covered with a veneering of slope deposits com- 

 posed of the disintegrated rocks and of vegetal mold, and this over- 

 placed material abounds, up to the quarry level, in artificial (h'bris. It 

 was at first thought that this association of the worked stones with 

 deposits of gravel might be of value as a means of determining the 

 age or period of occupancy, but examination develoi)ed the fact that 

 the gravel represented no definite period, its deposition extending 

 from the present back indefinitely into the past. 



In figure 3 a generalized view of the Piny branch quarry sites is 

 depicted; it will give a comprehensive idea of the configuration of the 



