Miscellanies. 205 



ble aspect. More recently, in the same country, other competent travel- 

 lers have experienced like difficulties, and, as I am informed, failed to 

 get any impressions whatever. Are these difficulties due to the antago- 

 nizing action of the negative rays upon the positive? 



4. On the Salt Steppe south of Orenburg f and on a remarkable 

 Freezing Cavern ; by Roderick Impey Murchison, Esq., Pres. G. S. 

 This salt steppe is distinguished from many of those which are inter- 

 posed between the Ouralsk and the Volga, or are situated on the Siberian 

 side of the Ural Mountains, by consisting not of an uniform flat resem- 

 bling the bed of a dried -up sea, but of wide undulations and distantly 

 separated low ridges; nevertheless it is, Mr. Murchison states, a true 

 steppe, being devoid of trees and little irrigated ty streams. The surface 

 consists of gypseous marls and sands, considered by the author to be of 

 the age of the zechstein,* and it is pierced in the neighborhood of the 

 imperial establishment of Uletzkaya Zatchita by small pyramids of rock 

 salt. These protruding masses attracted the attention of the Kirghiss 

 long before the country was colonized by the Russians, but it is only du- 

 ring a short period that the great subjacent bed has been extensively 

 worked. The principal quarries, exposed to open day, are situated im- 

 mediately south of the establishment, and have a length of three hundred 

 paces, with a breadth of two hundred, and a depth of forty feet. The 

 mass of salt thus exposed, is of great purity, the only extraneous ingre- 

 dient being gypsum, distantly distributed in minute filaments. At first 

 sight the salt seems to be horizontally stratified, but this apparent struc- 

 ture, Mr. Murchison states, is owing to the mineral being extracted in 

 large parallelopipedal blocks twelve feet long, three feet deep and three 

 wide. On the side where the quarry was first worked, the cuttings pre- 

 sented, in consequence of the action of the weather, a vertical face as 

 smooth as glass, but at its base there was a black cavern formed by the 

 water which accumulates at certain periods of the year, and from its roof 

 hung saline stalactites. The entire range of this bed of salt is not known, 

 but the mass has been ascertained to extend two versts in one direction, 

 and Mr. Murchison is of opinion that it constitutes the subsoil of a very 

 large area; its entire thickness also does not appear to have been deter- 

 mined, but it is stated to exceed one hundred feet. The upper surface 

 of the deposit is very irregular, penetrating, in some places, as already 

 mentioned, the overlying sands and marls. 



* His extensive surveys of Russia have convinced Mr. Murchison that rock-salt 

 and salt springs occur in all the lower sedimentary rocks of that empire from 

 great depths below the Devonian or old red sandstone system to the zechstein and 

 the overlying marls and sandstones. 



