Lesley.] 34 [May 



verted the outcrop edges of the limestone, as well as the limestone 

 clays and lime waters of the inflowings of the valley, into gypsum. 

 There must have been standing pools along these excavated faults, 

 or no deposits of solid gypsum and rock salt could have occurred. 

 And the want of such, in other parts of this and the neighboring 

 valleys has prevented similar deposits, especially in the great valley 

 east of "Wythe, where these lowest red rocks, with their sulphuret 

 ores of iron and lead, appear at the surface in great force ; and large 

 quantities of these ores have been converted into peroxide of iron 

 and carbonate of lead ; no doubt by the loss of sulphuric acid, gone 

 to produce gypsum, which has been carried off by the free drainage 

 of the country. None of the main parallel faults of the back valleys, 

 seem to bring these red rocks to the surface, except along the IIol- 

 ston ; and even here, it required the crushing of the surface rocks 

 along a supplementary anticlinal, to afford facilities, first for excava- 

 tion, and then for decomposition. 



It is possible, of course, that sulphur waters, issuing upwards 

 along the line of the anticlinal and cross faults, may have assisted in 

 the process ; but there is no need to call in their assistance to explain 

 the phenomenon, and such springs now are wanting elsewhere. On 

 the other hand, masses of sulphuret of iron, inclosed in workable 

 limonite ore, may be seen along the line, at Oarleton Hill, twenty 

 miles east of the Salt Works, and three miles east of large deposits 

 of limonite ore of workable quality. 



To account for the rock salt several hundred feet below the gypsum, 

 seems more difficult. It lies in solid form, mixed and interstratified 

 with compact red marl or clay, 200 feet below water-level ; and the 

 borings have gone down 176 feet further without reaching the 

 bottom. Into this deep lake, the drainage of the Upper Devonian 

 sandstones on one side of the fault, as well as of the Lower Silurian 

 limestones on the other, must have always run and deposited their 

 ■salt with mud and sand. But on top of the deposits of salt and mud 

 was thrown down a stratum of blue slate more than a hundred feet 

 thick ; and over this again, the 60 to 80 feet of gypseous clays, until 

 the lake was full. All this looks much more like a chemical than a 

 mechanical precipitation. 



The present connection of the mass of gypsum, mud, and salt with 

 the Holston River, through underground crevices beneath the ridge 

 of limestone which separates them, is apparent from the fact that 

 water in all the wells not only always stands at the same level, but at 

 the level of the river ; nor does the heaviest pumping alter it. 



The lower gypsum banks (Preston's) yielded in 1854, 2000 tons; 



