218 Pogue, Jr. — Geology and Structure of Volcanic Rocks. 



Art. XXI Y. — Geology and Structure of the Ancient Vol- 

 canic Rocks of Davidson County, North Carolina;* by 

 J. E. Pogue, Jr. 



Introductory. 



Preliminary statement. — The present article outlines the 

 more important, non-economic portions of a geological report, 

 presented as a thesis at Yale University in June, 1909, and 

 prepared under the direction of the North Carolina Geological 

 and Economic Survey. It is based upon three months' field 

 work done in the summer of 1908, and upon laboratory and 

 office work carried on during the autumn, winter, and spring \ 

 of 1908-09 in the Penological Laboratory of the Sheffield 

 Scientific School of Yale University. 



Location and geography. — The area described is known as 

 the Cid Mining District and is situated in the central portion 

 of North Carolina, within the Piedmont Plateau, and near the 

 western boundary of a great series of volcano-sedimentary 

 rocks, the Carolina slate belt, which crosses the state in a 

 northeast and southwest direction. The tract covers approxi- 

 mately 125 square miles, and was mapped in detail on the 

 scale 1 : 24,000. The average elevation above sea level is about 

 600 feet, and the range of elevations within the district is 

 about 300 feet. This range may be encompassed by long, 

 almost imperceptible slopes, not disturbing the appearance of 

 subdued relief ; or by sudden rises, with rugged topography 

 as a result. The district accordingly presents not only features 

 common to gently rolling, maturely dissected regions, but 

 also in places has a surface configuration comparable to moun- 

 tainous topography on a small scale. The drainage is into the 

 Yadkin Piver, which forms. the southwestern boundary of the 

 area and flows across the structure, cutting alike through hard 

 and soft formations. The minor streams, parallel to one 

 another and at right angles to the Yadkin, are in conformity 

 with the structure and have thrown into relief northeast trend- 

 ing ridges, locally called " mountains." The most conspicuous 

 of these is Flat Swamp Mountain, which forms a part of Flat 

 Swamp Pidge extending as a narrow ridge for nearly 7 miles 

 through the central portion of the district. The region is 

 sparsely inhabited and contains only a few small villages. It 

 has been of some importance as a mining center and contains - 

 the Silver Hill, Conrad Hill, Silver Valley, Emmons, Peters, 

 and other mines — of which the Silver Hill is the best known. 



Historical sketch. — It was not until 1894 that the presence 

 of rocks of volcanic origin within the Piedmont Plateau of 

 * Published by permission of the State Geologist of North Carolina. 



