the Gulf of California, and contains not far from 2,500 square miles.
The Colorado River, which has now flooded it, has been flowing along
to the east of it, emptying into the Gulf of California. The surface
of the desert is almost all level and low, some of it below the sea
level. Some few hundreds of years ago it was a bay making in from the
Gulf of California, and then served as the outlet of the Colorado
River. But the river carried a good deal of sediment, and in time made
a bar, which slowly and surely shut off the sea on the south, leaving
only a narrow channel for the escape of the river, which cut its way
out, probably at some time when it was not carrying much sediment.
Then the current became more rapid and cut its way back into the land,
and, in doing this, did not necessarily choose the lowest place, but
rather the place where the formation of the land was soft and easily
cut away by the action of the water.

"While the river was cutting its way back it was, of course, carrying
more or less sediment, and this was left along the banks, building
them all the time higher, and confining the river more securely in its
bounds. That is the Colorado River as we have known it ever since its
discovery. Meantime, the water left in the shallow lake, cut off from
the flow of the river, gradually evaporated--a thing that would take
but a few years in that country, where the heat is intense and the
humidity very low. That left somewhere about 2,000 miles of desert
land, covered with a deposit of salt from the sea water which had
evaporated, and most of it below the level of the sea. That is the
Colorado desert as it has been known since its discovery.

"Then, last spring, came the overflow which has brought about the
present state of affairs. The river was high and carrying an enormous
amount of sediment in proportion to the quantity of water. This