the salt. 



|5£ SCIENTIFIC NEWS. 



cured. The brine pits are in the centre of the town* being 

 situate in a narrow valley, through which the small river 

 Salwark flows. The prevailing rock about Droitwich is a 

 fine grained calcareo-argillaceous sandstone of a brownish 

 red colour, with occasional spots and patches of a greenish 

 blue. At Doder hill, in the immediate vicinity of the salt 

 pits, the rock appears to be a stratified sandstone of a 

 greenish gray colour, and more indurated than the red 

 rock. It also differs from this last in containing slender 

 veins of gypsum. 



Strata covering No new brine pits have been sunk for the last thirty years; 

 the only particulars therefore concerning the strata covering 

 the salt, which Mr Horner has been able to obtain, are de- 

 rived from Dr. Nash's History of Worcestershire, and from 

 an inhabitant pf Droitwich, who was on the spot when 

 the last pit was sunk. From these authorities it appears, 

 that the depth of from 35 to 45 feet below the surface is oc- 

 cupied by beds of gravel, of red marly clay, and of blue 

 and white stone. To these succeeds a bed of gypsum about 

 105 feet in thickness, immediately below which is what is 



River of salt. ca lled the river of salt, which is a stratum of nearly satu- 

 rated brine, 22 inches in depth, lying on a bed of rock salt, 

 the thickness of vvhich is unknown, uo borings having been 



Construction sunk in it to a greater depth than five or six feet. In con- 

 e pi S * structing the pits, the method is to sink a shaft about eight 

 feet square into the gypsum, and then to pierce this bed by 

 a borer four inches in diameter: the borer is known to have 

 passed through the gypsum by its suddenly dropping 22 

 inches, the depth of the river of salt. As soon as the borer 

 is withdrawn, the brine suddenly rushes tsp, and overflows 



Produce. a t the mouth of the pit. There are only four pits at pre- 



sent in all, and the annual quantity of salt which they af- 

 ford is about l600 tuns. 



1 ha brine. The brine from all the pits is perfectly limpid, and when 



in a large body has a pale greenish hue, similar to that of 

 . sea-water. To the taste it is intensely saline, but without 

 any degree of bitterness. The specific gravity differs in the 

 different pits, probably on account of the greater or less ac- 

 curacy with which the landsprings are stopped out: that of 

 perfectly saturated brineis equal to 1210'39 (waterbeinglOOO): 



that 



