Facts About the Salton Sea.
The socalled Salton sea on the borders of Mexico and lying immediately west of the Colorado river, is really no sea at all, but is formed by the seepage water that has found its way to the lower point in the widely extending desert lands. In former geologic times the head of the Gulf of California extended about 150 miles farther north than at present. The head of the gulf was cut oft, 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 there was little, if any water left in even the deepest part of the basin, about 300 ft. below sea-level. This water, by reason of concentration by evaporation, is extremely salt. It is difficult to determine where the water ends and the comparatively dry land begins, and 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. The course of the Colorado river is variable, and at one time and another the river flowed in different channels, some running towards the Salton sea depression. The cutting of an irrigation canal by the California Development company of New Jersey has inadvisedly undertaken to satisfy the local farmers afforded a quick descent from the river to the old Alamo channel, and at its next rise in 1904 the Colorado took this easy course towards Alamo, the result being a continuous flood, which so rapidly evaded the channel that by the spring of 1905 the entire river was passing by an abrupt turn to the westward down the Alamo channel, spreading out over the low ground, and converging northerly into the New river and the Salton sea. In its course towards the depression caused by the latter it gathered into narrow streams, gaining velocity with the increase of slope. These quickly began to establish for themselves definite beds by scouring out the soft material. At first slight falls of riffles were formed ; but later on these progressed backwards, and deepened as the channel was scoured out. It was seen that this back-cutting would not only destroy houses and fields, but would likewise involve the heads of the canals leading water out to the remaining agricultural lands. If these heads were cut off, and the water flowed violently down to the Salton sea through deep, steep-sided walls of earth, it would be ini possible to keep an adequate supply for the valley. The New Liverpool Salt Works and the main line of the Southern Pacific were endangered, and the railway officials took the matter in band. The engineering history of the work undertaken, as was told in these columns at the lime, extended over many months, and involved at least eight failures. It was easy enough to close or divert the stream to a point where it seemed possible to turn the river quickly. There.il difficulty lay in the increase of the speed of the flow, and the consequent more rapid erosion of the banks due to the construction of the channel by the works, and thus enormous gaps were being constanth created. The railway people drove piles across the break, and on these were laid parallel lines of tracks with ample and rapid switching facilities. Rock and stones in large numbers were dumped into the river more quickly than it could wash away the obstructions. In course of time the river rose and cascaded over the rock piles, and the river was raised 11 ft., small stone and gravel being dumped in immense quantities to fill up the interstices in the rock pile. The river was at last raised to a point where it began to flow down its former channel and less and less over the top of the rock heap. Then finer material was added and rapidly piled up on the accumulated rock mass. By this means the seepage through the rock pile was uqickly checked, and the barrier became effective. To prevent burrowing animals from making holes through the bank and undermining the works was the next thing accomplished, and now these extend from the head-works in the United States along the river, between it and the canal, a double row of dykes, the outer one being occupied by a railway. These extend in an unbroken line for 12 miles near the river and shut it off from the lowland to the west. The river side of this dyke is protected by a thick layer of gravel, and the railway affords immediate access to all parts, so that, if threatened, it will be possible to bring men and materials 10 check the floods from encroachment. Secondary dykes or cross-levees run from the main structure to certain subsidiary works, so that, if the outer main dyke is broken, or the water flows through, it will be ponded, for a while at least, against the inner line of defence, thus affording time to assemble the necessary equipment to fight another intrusion. The water needed icr irrigation of lands in the Imperial valley comes through the permanent head-works in the United Stales, follows down behind the dykes in the channel dug for the purpose, and then passes down the bed of the Alamo, enlarged during 1905. and 1906. It continues to a point where it is diverted into the canals of the settlers. The only water that escapes today is by seepage that not be avoided.