332 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
Colorado River. A great, if hot the greater, part of the county is 
below sea level, and the Salton Sea consists of the waste or seepage 
water which has found its way to the lowest point in the broad extent 
of depressed desert lands. 
In former geologic times the head of the Gulf of California ex- 
tended about 150 miles farther north than it does at present. Through 
causes to be later described the head of the gulf was cut off, leaving a 
depression filled with water but disconnected from the gulf by a 
broad area of low land. This water gradually diminished through 
evaporation until when the country was first discovered by the white 
man there was little if any of the water left in the deepest part of the 
basin, about 300 feet below sea level. This small remnant of water 
by reason of concentration by evaporation is extremely salt, so much 
so that a salt factory was established in its margin. 
Its original outline when discovered by white men is not accurately 
known, as the shores have such a gentle slope that with the covering 
of salt upon the margin it was difficult from a distance to determine 
where the water ended and the comparatively dry land began. It is 
possible that in some years the water may have entirely disappeared, 
leaving broad flat plains of white salt resembling in the distance the 
waves of an inland lake. 
PECULIAR GEOGRAPHY. 
The peculiar geographic conditions are determined largely by 
the fact that the Colorado River of the west, draining a consider- 
able portion of the arid regions of the United States, flowed not 
directly into the ancient head of the gulf but entered this body 
of water at a point about 100 miles below the head. The ex- 
tremely muddy river, carrying the washings from the mountains 
and plateaus of the north, deposited its load of sediment on reach- 
the salt water and spread this out in a broad alluvial fan, ultimately 
filling that portion of the gulf, cutting off the head and leaving it 
as a detached body of water. 
The Colorado River, flowing out upon the broad delta of mud, 
wandered in many channels at different times, occasionally turn- 
ing northward into the cut-off portion of the gulf and again 
turning southward into what is now the head of the present Gulf 
of California. There are thus left innumerable ancient channels, 
some of them intersecting and all of them with very tow banks over 
which the water pours in broad sheets in time of flood. 
The channel of the Colorado River, as known in historical times, 
and its proper channel as far as political divisions are concerned 
has a nearly southerly course, extending from about the location of 
the town of Yuma to a point near the head of the Gulf of California. 
