198 J. L. and H. D. Campbell — Wm. B. Rogers's 



explorations. In his State Eeport for 1837 he locates these 

 gypsum and salt beds in the upper part of his No. V — probably 

 Salina or No. 6 ,of Dana's series. In the Eeport of 1838 he 

 appears to have found the source of the gypsum at least, in the 

 limestones high up in his No. VIII. Then, in his notes pre- 

 pared in 1878 for Macfarlane's Eailway Guide, he says of the salt 

 and gypsum, that " Both deposits are probably referable to the 

 Sub-carboniferous period." If the solution of this problem 

 proved so difficult and perplexing to a profound and accom- 

 plished geologist like Prof. Eogers, it becomes us to approach 

 it with modesty. The question, however, seems to be still open 

 for discussion and for differences of opinion. 



In Prof. Dana's Manual of Geology, revised edition, 1880, p. 

 233, these deposits are referred to the Salina period, (6). Prof. 

 Lesley in his Eeport on the Geology of some of the southwest 

 counties of Virginia, 1871, regards the gypsum as produced by 

 the action of sulphuric acid or sulphuretted hydrogen from the 

 "Lower coal-measures," on the Lower Silurian limestones of the 

 Holston valley. His theory of the accumulation of the salt is 

 thus expressed : " The appearance of brine in such quantity and 

 of such strength must be considered a local phenomenon explain- 

 able without reference to the gypsum. Such an explanation 

 may be found in th^ very curious lake deposits of the little tri- 

 angular plain at Saltville ; a deposit evidently made in a deep 

 little lake or pond basin filled with red mud, and saturated with 



salt-water, gypsum drainings, etc The salt lies in a 



solid form, mixed and interstratified with compact red marl or 

 clay, 200 feet below the water-level of the Holston ; and the 

 borings have gone down, at the salt-works, 176 feet further 

 without reaching the bottom." If this be the true view, the 

 salt lake must have been formed and filled at a period subse- 

 quent to the production of the fissure above mentioned ; perhaps 

 in Permian or in Mesozoic time. If the question as to the 

 source of the salt of these beds is ever finally settled, that source 

 will most probably be found in the Sub-carboniferous ; in that 

 case the question becomes analogous to that in regard to the 

 same formation in Kanawha valley, where Eogers says, "from 

 these strata there is every reason to believe are derived the 

 saline ingredients which enrich the salt wells of that enterpris- 

 ing and prosperous region," (p. 373). 



Saltville is easily accessible by rail, and is surrounded by a 

 variety of interesting geological features, besides the beds of 

 gypsum and salt. 



Conglomerate Coal Croups, XII, E. (14 a). — The great con- 

 glomerate bed, called by English geologists, "Millstone Grit," 

 seems to have been regarded by the early geologists of this 

 country as one simple bed underlying the whole of the Appala- 



