Page:A Treatise on Geology, volume 1.djvu/228

 212 Europe, more frequent in a particular period of the earth's lamellar incrustation.

It is very important to remark that the salt lies always in small narrow patches; therefore, most evidently it was not produced by a general extrication from the marine water, and most probably is to be referred to local heat, or some other cause at great depths, or else to evaporation from a limited area, filled at intervals by the sea.

In order to discover the nature of these local peculiarities, we must compare the different salt deposits, with reference to their situation, accompanying minerals, and other leading circumstances.

So little relation appears between the actual form of the ocean and the boundaries of the ancient seas in which the strata were formed, that it will probably be of little use to notice the geographical situation of the beds of rocksalt as compared to the present distribution of land and water. The salt mines of England are in very low ground: those of Wieliczka lie at the foot of the Carpathian mountains on the north, and those of Cardona beneath the Pyrenees on the south: many mines in Wurtemburg and central Germany are in the midst of rather elevated plains; and at Bex salt lies in an ancient valley, some distance above the Lake of Geneva, itself 1000 feet above the sea. With respect to the present ocean, the mines of England and Cardona are near to it, but the others far distant.

It does not seem possible to extract from such a discordant assemblage of facts any general character of situation depending on the present distribution of land and water, nor perhaps has it ever been attempted; but because in the instance of the Cheshire salt district, the local circumstances are such as to have given occasion for Dr. Holland's hypothesis, that the salt there was derived from the neighbouring sea, it will be worth while to discuss the formation of that salt basin separately.

The Cheshire deposits of salt lie along the line of the valley of the river Weaver, in small patches, about