The waters of the Dead Sea are thus in the condition of having already deposited almost all their gypsum, as well as the greater part of the salt they originally contained.  They are, in fact, much like sea water which has been boiled down till it has reached the state of a thick salty liquid; and though most of the salt is now already deposited in a deep layer on the bottom, enough still remains in solution to make the Dead Sea infinitely salter than the general ocean.  At the same time, there are a good many other things in solution in sea water besides gypsum and common salt; such as chloride of magnesia sulphate of potassium, and other interesting substances with pretty chemical names, well calculated to endear them at first sight to the sentimental affections of the general public.  These other by-contents of the water are often still longer in getting deposited than common salt; and, owing to their intermixture in a very concentrated form with the mother liquid of the Dead Sea, the water of that evaporating lake is not only salt but also slimy and fetid to the last degree, its taste being accurately described as half brine, half rancid oil.  Indeed, the salt has been so far precipitated already that there is now five times as much chloride of magnesium left in the water as there is common salt.  By the way, it is a lucky thing for us that these various soluble minerals are of such constitution as to be thrown down separately at different stages of concentration in the evaporating liquid; for, if it were otherwise, they would all get deposited together, and we should find on all old salt lake beds only a mixed layer of gypsum, salt, and other chlorides and sulphates, absolutely useless for any practical human purpose.  In that case, we should be entirely dependent upon marine salt pans and artificial processes for our entire salt supply.  As it is, we find the materials deposited one above another in regular layers; first, the gypsum at the bottom; then the rock-salt; and last of all, on top, the more soluble mineral constituents.

The Great Salt Lake of Utah, sacred to the memory of Brigham Young, gives us an example of a modern saline sheet of very different origin, since it is in fact not a branch of the sea at all, but a mere shrunken remnant of a very large fresh-water lake system, like that of the still-existing St. Lawrence chain.  Once upon a time, American geologists say, a huge sheet of water, for which they have even invented a definite name, Lake Bonneville, occupied a far larger valley among the outliers of the Rocky Mountains, measuring 300 miles in one direction by 180 miles in the other.  Beside this primitive Superior lay a second great sheet—­an early Huron—­(Lake Lahontan, the geologists call it) almost as big, and equally of fresh water.  By-and-by—­the precise dates are necessarily indefinite—­some change in the rainfall, unregistered by any contemporary ‘New York Herald,’ made the waters of these big lakes shrink and evaporate.