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 Alice in
Wonderland, till there was absolutely nothing left of it; Lake
Bonneville shrank till it attained the diminished size of the existing
Great Salt Lake.
Pages:
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338