1880.] 155 



Mr. Lesley described the results of a recent visit to Salt- 

 ville, in Virginia, made by Mr. Henry Carvil Lewis, of 

 Germantown, on the suggestion that Tertiary shells might 

 be found at the eastern corner of the little plain on which 

 the salt and gypsum works stand. 



Mr. Lewis reported that he had not only carefully collected all the 

 univalves and bivalves of the locality but submitted them for examination 

 to Mr. Tryon, of the Academy of Natural Sciences, who pronounced them 

 all recent, and one of them as a species nowhere yet seen except in the 

 Houston river, which flows along side of the plain, and the waters of which 

 communicate with the wells, as described by Mr. Leslej?^ some years ago. 



Mr. Lewis had made a comparative collection of the same shells from the 

 banks of the Houston and found the two suits identical. 



On causing a number of pits to be dug he was surprised to find the sur- 

 face stratum (three feet deep) to be a layer of these shells, most of the unios, 

 &c., broken, but the gasteropods whole, mixed with pottery and embers. 

 It is evidently a kitchen trasTi deposit. The shells did not extend beyond 

 the area of the pottery. The Indians broke up the univalves to mix with 

 the clay of the pottery, but the gasteropods must have been used only for 

 culinary purjioses. 



He found under the layer of shells and pottery a layer of local drift clay, 

 several feet thick, resting on the red gypsum salt muds, which are several 

 hundred feet deep and occupy a basin a mile wide, eroded along an anticlinal 

 arch of Lower Silurian limestones, the outcrops of which form the hill 

 walls of the little enclosed secluded valley. The rocks dip 20° to 30° 

 south-east ; and from 50° to 60° north-westward towards the Houston river, 

 outside of the enclosure. This erosion must have commenced when the Ap- 

 palachian continent, crowned by Permian deposits, rose from the sea on the 

 first construction of the anticlinal and synclinal folds. The salt clays then 

 are probably of Trias age. That the gypsum is the result of the decompo- 

 sition of the limestone layers is plainly shown in the shaft and tunnel 

 workings ; and it is confined to the walls of the basin, against which the 

 horizontal salt-muds lie nonconformably. 



Mr. Lesley embraced this occasion to make some remarks 

 in opposition to the conclusions of Prof. Stevenson, express- 

 ed in his valuable Notes on South Virginia, read before this 

 Society, Aug. 20, respecting the comparatively recent date 

 of the great Virginia faults. 



Prof. Stevenson does not positively assert that the faulting has succeeded 

 the flexing by a longer or shorter interval of geological time, but he says : 

 "It seems not wholly improbable that the faults are of later date than the 

 disturbance which produced the comparatively gentle synclinal between 



