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. Lake Lahontan shrank away like A