HOLMES] GEOLOGIC DISTRIBUTION OF STONE 137 



up into rather large fragments; thus it is that we liave many hirge 

 quartzite bowlders deposited in the valley about Washington and 

 below, the sizes diminishing toward the sea. Between the Blue ridge 

 and tidewater the river crosses a belt of gneiss rocks intersected by 

 many veins of quartz. This latter rock is hard and brittle, and breaks 

 up into small fragments, which, when rounded, are usually of the size 

 denominated pebbles. These were taken up by the waters in countless 

 numbers and distributed with the quartzite bowlders from Washington 

 to the sea. But the quartz is hai'der than the quartzite and resisted 

 the erosive agents more successfully, so that after the quartzite disaj)- 

 pears there are still quartz pebbles in plenty. 



The other stream, the Patuxent, has a limited drainage and does 

 not cross the quartzite belt but drains the quartz-bearing zone. Below 

 the point of its entrance into the tidewater country at Laurel, we find, 

 of the flakable stones, chiefly quartz in small fragments; lower down 

 all are well rounded, lornung pebbly gravels. It is thus seen that 

 nature has selected the rocks used by the tidewater peoples and has 

 distributed them in groups varying with original location, with hard- 

 ness, with toughness, with shape, and with size. 



GEOLOGY AND ART 



The effect of the natural conditions of distribution on the stone art 

 of the various districts was necessarily prououuced. One community 

 located conveniently to deposits of large bowlders used large stones, 

 and the tools shaped from them average large. Another community 

 located in a pebble-bearing district utilized pebbles, so far as they are 

 capable of utilization, and this people had few large tools and many 

 small ones, the average size being small. Dwellers in quartzite-bearing 

 districts had quartzite tools, those having quartz deposits had quartz 

 tools, and those residing near the base of the highland had many 

 varieties of stone and hence used a much greater diversity of stone 

 tools, since the working (lualities or capacities of each stone vary from 

 the rest. 



As a result of these conditions the tidewater Potomac is rich in 

 chipped tools, both of quartzite and of quartz, of home production. 

 The Patuxent yields a large percentage of quartz tools, most of which 

 are native. The Potomac yields to the collector a large percentage of 

 large tools, the Patuxent a large percentage of small ones. These 

 remarks relate to the native varieties of material and implements 

 made from them. Exotic materials had their own peculiar distribu- 

 tion, which will be examined further on. 



Nearly all rude, bulky implements of chipped stone, and all failures 

 or rejects of manufacture, are, as a matter of course, found on or near 

 the sites from which the raw materials were derived. Rejects are 

 large and clumsy on the upper tidewater Potomac because of the large 

 size of the bowlders available; they are small on the Patuxent because 

 the pebbles utilized were small. 



