Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/72

 60 recede from the sea, may perhaps be admitted as another argument in behalf of the opinion.

The principal objection to the theory undoubtedly is, the non-existence of marine exuviæ either in the rock-salt, or in the adjacent strata of clay; a fact very difficult to connect with the idea of a deposition from the waters of the sea. Other objections, though perhaps of less moment, arise from the appearance of the earthy salts in smaller proportion in the rock-salt than in sea water; from the apparently partial deposition of the beds, and from the difficulty of explaining the formation of the figured appearances which occur in the substance of the rock. These circumstances, however, will by no means authorize us to reject the general idea which has been given of the origin of this mineral, strengthened as it is by the situation and appearances observed in the foreign salt mines, where the proofs of marine deposition are still stronger than those presented in the Cheshire district.

I confess I see no sufficient reason for supposing the action of subterraneous or internal heat in the formation of the beds of fossil salt. It appears probable that a deposition of muriate of soda from the confined waters of the sea might have taken place without the intervention of this agency, and there are no appearances either in the beds of salt, or in the clays accompanying them, which render it necessary to have recourse to the supposition in question. It must be acknowledged, however, that it is difficult to give a satisfactory account of the consolidation of the beds of salt; nor do I know any opinion on this subject, which can be considered altogether free from objection. A more enlarged discussion of these theoretical points may be found in the Appendix to the Report of Cheshire, before alluded to.

In dwelling thus minutely upon the natural history of the Cheshire rock-salt district, I am not aware that I have gone further