A part of its burden of silt was laid down over the northern portion of the gulf, and a part of it was carried by the force of the current far down into the great body of water and was piled up ninety miles below the present boundary line between Mexico and the United States. This bank was about sixty miles long, extending in an easterly and westerly direction. Along the right side of the current was formed a lateral embankment, which eventually shut off the river from its former inlet into the gulf and directed it to its present mouth, some two hundred miles lower. This, joining with the sixty-mile embankment, severed one portion of the gulf from the main body and left an inland sea where now is the desert. Then the thirsty sun drank up the waters of this sea and left the land of desolation. How long ago all this happened is a matter of conjecture. There are many places on the boundaries of the desert where the ancient beach-line may be traced long distances. Here are found numerous shells and corals. Many of the shells are unbroken, and one might almost believe, to look upon them, that they were tossed there by the restless waves no longer ago than yesterday. The varieties of shells and of sea relics correspond very closely with those now abounding in the sea. [Illustration: ANCIENT SEA BEACH, COLORADO DESERT, NEAR COACHELLA From photograph by C. C. Pierce & Co.] There are evidences that the desert has been dry land many centuries. Upon its breast are found Indian pottery and implements of a style and pattern antedating those in use at the time the white man reached this country. Then, too, as far back as the sixteenth century, when the earliest exploration of that region was made, the desert-dwelling tribes seem to have been thoroughly established in the territory once occupied by the gulf. It doubtless required centuries, after the waters were cut off from the region, to dry up the inland sea and make it possible for man to enter in and occupy the territory. It is the belief of some scholars that the land was submerged when the first Spanish explorers reached the coast. In support of this theory they point to certain maps which show the gulf as covering that region. A map of the early navigators recently in the possession of General Stoneman of the United States Army, which was obtained by him in the City of Mexico, shows the Gila River as entering the gulf, whereas the Gila River now enters the Colorado River ninety miles north of the present mouth of the Colorado.