Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean: Vol. 5, Pt. 2

FORMATION OF THE ANCIENT LAKE-PROBABLE EVAPORATION OF THE WATER.
flowed along the line of banks or terraces near Cook's Well and the Alamo, and after depositing
its silt in the quiet water of the lake, escaped into the Gulf, at some point near or below the
present entrances to New River. With the immense quantities of silt that the Colorado brings
down, even now, such conditions could not long remain, and the river must have been turned
towards the more open waters of the Gulf by the resistance of its own depositions. After the
lake had become deprived of its supply of water from the river, and its communication with the
Gulf became closed, except, perhaps, at seasons of freshets, it must have undergone rapid
evaporation, especially in that region of violent, arid winds, pouring in from the surrounding
deserts and over the mountains from the sea. The great rapidity of evaporation in the climate
of the Tulare Valley has been shown, and it is not difficult to comprehend that this cause was
sufficient to remove all the water from the lake in the course of a few years.
Some of the conditions which have been detailed as probable are still found to exist. The
Colorado yet continues to overflow at seasons of high water, and the water runs backward for
sixty miles, and forms a chain of small lakes or ponds; the water in these evaporates rapidly,
and disappears soon after the supply ceases. We find an extensive area of low and marshy land
around the head of the Gulf, which is annually overflowed -nd covered by quantities of silt spread
out upon it by the Colorado. Father Consag, who made the first survey of the Gulf in 1746,
ascending as far as the mouth of the Colorado, describes the land about it as low and marshy;
the mud being red, and so soft that it would not support the men when they stepped out upon it. 1
The enormous quantities of silt carried down by the river is shown not only by the dark-red
color of its water, but by the discoloration that it produces in the water of the Gulf, which was
formerly called the Vermillion Sea, probably from its red color.
Changes very similar to this displacement of the waters of the Gulf and the formation of a
lake have taken place in other parts of the world, and it is not at all surprising that the depo sition of sediment by the Colorado should produce the results which have been effected, when we
consider the enormous amount of silt brought down by the 3Mississippi, the Nile, Ganges, and
other rivers, and the rapid increase of their deltas. According to the observations of W. K.
Loftus,2 the head of the Persian Gulf, within a comparatively recent period, extended, certainly,
two hundred and fifty miles further to the northwest than the present mouth of the combined
stream of the Tigris and Euphrates, and one hundred and fifty miles beyond the junction of
these two great rivers at Korna. The alluvial deposit from these rivers is said to increase a
mile in thirty years; 3 and Sir Charles Lyell gives a statement, made by Colonel Rawlinson,
that the delta of those rivers has advanced two miles in the last sixty years, and is supposed to
have encroached about forty miles upon the Gulf of Persia in the course of the last twenty-five
centuries. 4 Very great changes have also been produced at the mouths of the rivers which
enter the Adriatic Sea. It is stated by Lyell that "there is an uninterrupted series of recent
-accessions of land more than one hundred miles in length, which, within the last two thousand
years, have increased from two to twenty miles in breadth." 5 If these great accessions of land
had been confined to the mouth of one stream many miles below the head of a narrow gulf, a
lake would most certainly have resulted. If the Colorado had emptied into the head of the
Valley of the Gulf in the same manner as the Tigris and the Euphrates enter the Persian Gulf,
I Father Fernando Consag, in Venega's History of California, ii., p 144.
2 Quarterly Journal of the Geological Society of London, xi., 43, p. 251.
3 Ainsworth and Rawlinson, Proceedings Geographical Society, 1850.
4 Lyell's Principles of Geology, p. 285.
5 Principles, p. 256.
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