Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/413



The great body of the salt forms a rugged precipice, which is reckoned between 400 and 500 feet in height at the upper extremity of the valley, and is covered by a thick bed of the clay above mentioned.

The precipitous form is partly owing to the manner in which the mine has been wrought for a series of ages. There is no excavation; but the salt has been procured by working down perpendicularly as in an open quarry. The lowest part of the present works has a solid floor of pure salt which is not above the level of the bottom of the valley where no salt is found; but the real depth of the bed of salt has never yet been ascertained. The upper surface of the salt is not level; but appears irregularly elevated, according to the general outline of the hill in which it occurs.

The salt has been usually represented as forming an entire mountain: but though it here appears supplying the place of common rock, yet from its being confined to this valley, and not attaining so high a level as the surrounding hills, it would seem more correct to consider it as a mass or bed of salt filling up a valley, than as constituting a mountain, which according to some authors is a league in circumference. These dimensions could only be obtained by considering the neighbouring heights as formed of this mineral; a supposition not countenanced by my personal observation, nor by the best information which I could collect on the spot.

The surfaces of the salt precipice which have been long exposed to the weather are not smooth, but cut into innumerable shallow channels, running in a tortuous manner, and divided from each other by thin edges, often so sharp as to cut the hands like broken glass.