The thickness of the beds in each salt deposit of course depends entirely upon the area of the original sea or salt-lake, and the length of time during which the evaporation went on.  Sometimes we may get a mere film of salt; sometimes a solid bed six hundred feet thick.  Perfectly pure rock-salt is colourless and transparent; but one doesn’t often find it pure.  Alas for a degenerate world! even in its original site, Nature herself has taken the trouble to adulterate it beforehand.  (If she hadn’t done so, one may be perfectly sure that commercial enterprise would have proved equal to the occasion in the long run.) But the adulteration hasn’t spoilt the beauty of the salt; on the contrary, it serves, like rouge, to give a fine fresh colour where none existed.  When iron is the chief colouring matter, rock-salt assumes a beautiful clear red tint; in other cases it is emerald green or pale blue.  As a rule, salt is prepared from it for table by a regular process; but it has become a fad of late with a few people to put crystals of native rock-salt on their tables; and they decidedly look very pretty, and have a certain distinctive flavour of their own that is not unpleasant.

Our English salt supply is chiefly derived from the Cheshire and Worcestershire salt-regions, which are of triassic age.  Many of the places at which the salt is mined have names ending in wich, such as Northwich, Middlewich, Nantwich, Droitwich, Netherwich, and Shirleywich.  This termination wich is itself curiously significant, as Canon Isaac Taylor has shown, of the necessary connection between salt and the sea.  The earliest known way of producing salt was of course in shallow pans on the sea-shore, at the bottom of a shoal bay, called in Norse and Early English a wick or wich; and the material so produced is still known in trade as bay-salt.  By-and-by, when people came to discover the inland brine-pits and salt mines, they transferred to them the familiar name, a wich; and the places where the salt was manufactured came to be known as wych-houses.  Droitwich, for example, was originally such a wich, where the droits or dues on salt were paid at the time when William the Conqueror’s commissioners drew up their great survey for Domesday Book.  But the good, easy-going mediaeval people who gave these quaint names to the inland wiches had probably no idea that they were really and truly dried-up bays, and that the salt they mined from their pits was genuine ancient bay-salt, the deposit of an old inland sea, evaporated by slow degrees a countless number of ages since, exactly as the Dead Sea and the Great Salt Lake are getting evaporated in our own time.