280 Beviews — Mock Salt. 



has been obtained from the springs by sinking vertical hollow logs 

 over their sources along the stream-bed and pumping the salt water. 

 During the past three years it has been proved by boring that vast 

 masses of rock-salt occur beneath some, if not all, of the salines, 

 and in various parts of the State. At one spot in South Louisiana 

 the drill entered rock-salt at a depth of 334 feet and continued in it 

 without change to a depth of 2090 feet ; in another, a thickness of 

 2263 feet of salt was passed through, and after a further depth of 

 non-saliferous strata had been passed through, salt was again en- 

 countered of unknown thickness. At this latter locality, Petite Ansa, 

 the amount of salt present is estimated at about 2,000,000,000 tons ; 

 and, as the author remarks, "no one can claim to have but the faintest 

 idea of the true value of the huge masses of pure rock-salt stored away 

 in the ' islands ' and salines of Louisiana." The term ' island ' is 

 here applied to the mounds or domes beneath which the salt is 

 obtained by mining. 



The salt occurs in the Eocene and Quaternary strata, which consist 

 of clays, loams, sands, and gravels, with occasional limestones and 

 lignites. The details vary much, and in one locality there was found, 

 at successive horizons, limestone, gypsum, occasional oil and gas, and 

 finally below, with unknown thickness, rock-salt. All the mounds 

 and salines thus far prospected have shown the existence, singly or 

 in association, of salt, gypsum, sulphur, dolomite, petroleum, hot 

 sulphurous and saline waters, etc. 



The origin of the domes was attributed by Hager to upthrust of 

 faulted masses of Cretaceous and Carboniferous rocks beneath the 

 yielding Tertiary deposits, in which the faulting of the strata below 

 was replaced by simple anticlinal folding. The pressure of gas, oil, 

 water, and of hypothetic igneous plugs have also been referred to as 

 agents likely to account for the phenomena. The present author and 

 his associates attribute the uplifting to the power of growing crystals. 

 They admit that they have not at present determined the power 

 of growing crystals, but they infer that it will be found to be of 

 the same order of magnitude as the resistance which the crystals 

 offer to crushing stresses. A 4 inch cube of crystallized salt, which 

 had been mined with dynamite, and was apparently more or less 

 inclined to crumble, showed no sign of crushing when put under 

 a pressure of 50,000 lb., the limit of the small hydraulic press 

 used. Further experiments are, however, desirable. The very 

 restricted areas occupied by the salt-masses compared with their 

 thickness is a remarkable feature. With regard to the age of the 

 domes the author considers that they were formed whenever conditions 

 were favourable, and that the various mineral deposits of salt, oil, 

 sulphur, gypsum, etc., though often flowing into Tertiary or Quater- 

 nary reservoirs, originated in beds belonging to earlier periods of 

 the earth's history. 



A valuable record of salt deposits and brine springs in other parts 

 of the world occupies about two-thirds of this report ; and it is 

 remarked that while in France and Germany there are works that 

 cover somewhat the same ground, there is no recent English work 

 on the subject. 



I 



