294 ROCK SAVT. 



evaporation account for the concretionary structure 

 of the salt of Cheshire. 



To these difficulties it must be added, that the 

 depth of sea water required to produce, in this man- 

 ner, some of the larger masses known in Europe, is 

 incomprehensible. It might also be asked, why ma- 

 rine organic bodies have never been found in or near 

 it, and wherefore it is accompanied by gypsum. As it 

 is, lastly, true, that the strata which lie above it have 

 been deposited under the ocean, it is impossible to 

 comprehend how, under these circumstances, evapo- 

 ration could have taken place. The subject is beset 

 with difficulties ; fortunately for the cultivators of a 

 science, which would lose the greater part of its attrac- 

 tions were there nothing left to explain. As to the 

 theory which derives it from volcanic actions, it 

 seems useless to discuss such a question, when no 

 volcanic rocks accompany these deposits in the sand- 

 stone, and when, with some very slender exceptions, 

 deposits of salt are not found attending on this class 

 of rocks. Were this the cause, it would remain also 

 to be explained why it is limited to the red marl. 



