174 Rock Salt and Salines of the Hols ton. 



from two hundred to three hundred and eighty six feet. All the 

 wells at the present site are within an area of three hundred feet; 

 to this area, and the original wells one mile northeast of the for- 

 mer, the discovery of salt water has been confined. The same 

 general section is presented in all the wells and borings, the up- 

 per eighteen or twenty feet consisting of the before mentioned 

 alluvium, to which succeed alternating strata of red and blue clay 



and gypsum, the latter generally predominating, and which con- 



tinue to the depth at which water is found, usually about two 

 hundred feet. Throughout the valley already described, gypsum 

 is found, generally at the depth of from eighteen to twenty feet. 

 Further east the gypsum crops out, being underlayed with red 

 and blue shales ; immediately overlying the gypsum is a fetid 

 crystalline limestone of a dark color, quite cellular, the cells be- 

 ing filled with crystals of carbonate of lime. At times the gyp- 

 sum is separated from this rock by a thin seam of black pyritous 

 slate. The gypsum is laminated, the plane of lamination having 

 a general parallelism with that of its dip, which corresponds with 

 that of the associated rocks, which is here highly inclined, show- 

 ing that the deposition of the gypsum was anterior to the present 

 disturbed condition of the rocks. The exposed portion of the 

 gypsum is from twelve to twenty feet in thickness. The gyp- 

 sum, unlike that of New York, is a nearly pure sulphate of lime; 

 sometimes crystalline, sometimes granular, usually white, except 

 when exposed to infiltration from the shales, when it has a slight 

 ferruginous tinge, which is usually the case in the upper portion, 

 where it is also more distinctly crystalline. Occasionally, it con- 

 tains thin seams of a dark smoky color, and sometimes radiating 

 crystals of the same hue. Running through the mass are fre- 

 quently seams of beautiful fibrous gypsum. Well defined plates 

 of selmite are rare. Gypsum of this general character occurs 

 over a region of country of about half a mile in breadth and fif- 

 teen miles in length ; it is generally worked to the depth of from 

 twelve to twenty five feet, without being passed through ; at 

 several localities it has been ascertained to extend to the depth of 

 two hundred and three hundred feet, and in one instance over 

 four hundred feet. 



In 1840, in sinking a shaft at Saltville, after passing through 

 the usual thickness of alluvium, and alternating strata of red and 



blue clay and gypsum, nearly forty feet of which was solid gyp- 



