Rock Salt and Salines of the Holston. 175 



sum, salt rock* was met with at the depth of two hundred and 

 twenty feet, and continued to the bottom of the shaft, two hun- 

 dred and seventy three feet, and was ascertained by boring to 

 extend to the depth of three hundred and eighty six feet, with- 

 out being passed through. In this well no water was met with. 

 Nothing is known respecting the shape or extent of this deposit, 

 except what is learned from the above mentioned shaft, — that it 

 is there over one hundred and sixty six feet in thickness ; it is 

 however quite local in some directions, as it is not found in the 

 neighboring shafts. If it is however, as seems most probable, the 

 source of the brine, which has been worked for so many years un- 

 diminished in strength and quantity, it must be quite extensive. 

 Much interest is imparted to this salt by its being the only fossil 

 salt yet discovered in the United States. The salt is irregularly 

 intermixed with red and blue clay and small fragments of shale, 

 the salt usually predominating ; occasionally the former are absent. 

 These impurities, mechanically intermixed with the salt, were 

 much more abundant in the upper portion of the bed, which was 

 almost entirely free from them at the bottom of the shaft. The 

 salt is compact, semi-crystalline, generally of a deep ferruginous 

 color, though occasionally of a delicate flesh tint, and more rarely 

 it is entirely free from coloring matter. 



The planes of the shales intermixed with the salt have not 

 that parallelism with each other which gravity would impart to 

 them if deposited under quiet circumstances ; and their irregular 

 distribution through the salt, making with each other every con- 

 ceivable angle, indicates agitation at the period of their deposi- 

 tion. Gypsum is occasionally interlaminated with the salt, and 

 sometimes occurs in it, in fibrous crystals, more or less impreg- 

 nated with salt. The salt is anhydrous, and nearly a pure 

 chloride of sodium, as the following analysis will show. 

 Peroxide of iron, .... 0.470 gr. 

 Sulphate of lime, .... 0.446 

 Chloride of calcium, ... a trace. 

 " sodium, . . . 99.084 



The local occurrence of a fault, the generally disturbed con- 

 dition of the rocks, and the anhydrous nature of the salt, all argue 

 the action of heat contemporaneously with, or subsequently to 



* See the notice of this fact, published in this Journal, 1841, Vol. xli, p. 214. 



