128 



and clays, and perhaps twice that distance to find soils unques- 

 tionably residual from ancient rocks. A hill about a mile and 

 a half north of Harlem is capped with the purple rock but 

 has angular pieces of quartzite, some about a foot long, on 

 its southern slopes and even farther south. The rock in ques- 

 tion occurs on comparatively level uplands, and does not seem 

 to form continuous ledges of any considerable extent, but is 

 a sort of surface crust, commonly only a foot or two in thickness 

 and broken up into fragments ranging from about the size of 

 a pea to that of a man's head, and in some places covering 

 the ground so thickly as to prevent plowing. It is often mottled 

 with white, in much the same way as many of the non-cal- 

 careous clays of the coastal plain, and it is probably only an 

 indurated clay. The larger pieces have been used locally for 

 curbing and foundations, and there is one handsome modern 

 house in Harlem with outer walls built entirely of this rock 

 (perhaps the only one of its kind in the world), and another 

 with porch columns constructed of it. Smaller fragments are 

 used for road material. 



In some respects it strongly resembles the Altamaha Grit, 

 which characterizes one of the regions farther down in the 

 coastal plain, ^ but that forms thick ledges, usually on hillsides 

 or near streams, and is more brownish in color, much like pine 

 bark. All the purple rock that I have seen is within a mile or 

 two of Harlem, in the counties of Columbia and McDuffie; 

 but of course there may be other occurrences of it at a greater 

 distance. Its area seems to correspond approximately with 

 that of the "Greenville gravelly loam"'* described by C. N. 

 Mooney and A. E. Taylor in their soil survey of Columbia 

 County, published by the U. S. Bureau of Soils in 1912. The 

 areas of that soil there mapped are all within two or three miles 

 of Harlem, and their aggregate extent in the county is put at 

 1600 acres. 



The vegetation on the purple rock is much less unique than 

 that on the Altmaha Grit, and shows nothing remarkable except 

 in the abundance of certain species that are scarcer elsewhere 

 and the variation of some others from their typical forms, 



3 See Torreya 4: 140; 6: 242; 11; 97. 



* This designation is rather misleading, for the purple rock seems to have 

 no gravel in it, and it has little in common with any rock or soil near Green- 

 ville, Ala. (from which that soil series name seems to have been derived). 



