The Coahuila Valley, in which Salton Lake is situated, is 90 miles long and from 10 to 30 wide. It separates the San Bernardino range of mountains from the San Jacinto, and forms a part of the great Colorado Desert in San Diego County. In its deepest portions it is 275 feet below the level of the sea; the area of the depressed region is over 1,600 square miles. In its northern portion the valley consists of sandhills and dunes, the former caused by the accumulation of the sand around the scrub and bushes growing in the desert. The southern portion is bare clay. On the borders of the desert palm trees of the fan palm variety occur in a few scattered clusters. The Southern Pacific Railroad passes through the valley on its way to Yuma. In that part of the depression adjacent to the railroad station of Salton is a salt marsh, where the New Liverpool Salt Company’s works are located, and where a fine quality of table salt is produced, containing, according to an analysis made by Thomas Price, of San Francisco: Chloride of sodium 94.68 per cent. Calcium sulphate .77 per cent. Magnesium sulphate 3.12 per cent. Sodium sulphate .68 per cent. Water .75 per cent. 100.00 per cent. The brine from which the salt is obtained shows a density of 27° Baumé. The company’s works are situated about 3,000 feet west of the railroad track, and consist of the salt mill and a large storehouse, connected by track with the main line. This branch line extends into the marsh a distance of over 10,000 feet. Beyond the end of the track a borehole was sunk by the company, with the expectation of obtaining water, to a depth of 300 feet, when the work was interrupted. The strata passed through during the sinking throw some light on the past condition of the desert depression, as well as furnishing some points that may have a bearing on the flooding of this section. The top covering consists of 6 inches of black mud, resting on a crust of chlorides of sodium and magnesium, 7 inches in thickness. The drill on passing through this crust dropped through 22 feet of a black ooze, containing over 50 per cent of water. Tests of the ooze made at the State Mining Bureau laboratory showed it to consist largely of chlorides and carbonates of sodium and magnesium, the soda salts predominating, besides fine sand, iron oxide, and clay, and a small amount of organic matter. The ooze was resting on a hard clay bottom, through which the drill passed for the entire remaining distance, only varied by two or three streaks of cement. From the shore line of the marsh toward the adjacent mountain ranges, the soil consists of a fine sand, containing clay and a notable quantity of mica, and is strewn with well-preserved shells of _Planorbis ammon_, Gould, _Physa humerosa_, Gould, and _Amnicola protea_, Gould.