Scientific American Supplement, No. 508, September 26, 1885 | Page 6

the surface through a pipe running down from the top of the shaft, whereas the Cornish pumps are run by huge steam engines.
By means of the hydraulic pumps they were enabled to sink the shaft to the 2,600 level, and extended the Cornish pumps to that point, where another set of hydraulic pumps was put in. They then sunk the shaft to the 2,800 level, when they ran another drift westward, and tapped the vein. The prospects at this depth in the Hale & Norcross and Chollar mines were so encouraging that the management decided to sink the shaft to the depth of 3,000 ft. On reaching the 3,000 level, they ran a third drift through to the vein. The distance from the shaft to the east wall of the vein was found to be only 250 ft. At the depth of 3,000 ft. they put in one of the pair of hydraulic pumps that is to be set up there. The second pump is now arriving from San Francisco, and as soon as the several parts are on the ground, it will be at once put in place alongside its fellow on the 3,000 level. This additional pump will increase the capacity from 600,000 to 700,000 gallons in twenty-four hours, or about forty-five miners' inches.
Owing to the excellent showing of ore obtained on the 3,000 level by the Hale & Norcross Company, and to the continuation of the ore below that level (as shown by a winze sunk in the vein), the management determined to sink the shaft to the vertical depth of 3,200 ft. It is now 3,120 ft. deep, and it is safe to say that it will reach the depth of 3,200 ft. early in September, when it will lack but eighty feet of being as deep as the shaft at Przibram was at the time of the great festival. Although the shaft is of great size--about thirty feet by ten feet before the timbers are put in--the workmen lower it at the rate of about three feet a day, in rock as hard as flint.
The hydraulic pump now working at the 3,000 foot level of the shaft is the deepest in the world. In Europe the deepest is in a mine in the Hartz Mountains, Germany, which is working at the depth of 2,700 feet. It is, however, a small pump not half the size of the one in the Combination shaft. Although these pumps were first used in Europe, those in operation here are far superior in size, and in every other respect, to those of the Old World, several valuable improvements having been made in them by the machinists of the Pacific coast.
The capacity of the two Cornish pumps, which lift the water from the 2,900 foot level to the Sutro drain tunnel (at the 1,600 level), is about 1,000,000 gallons in twenty-four hours, and the capacity of the present hydraulic pumps is 3,500,000 gallons in the same time. They are now daily pumping, with both hydraulic and Cornish pumps, about 4,000,000 gallons, but could pump at least 500,000 gallons more in twenty-four hours than they are now doing. The daily capacity with the hydraulic pump now coming, and which will be set up as mate to that now in operation at the 3,000 foot level, will be 5,200,000 gallons.
The water which feeds the pressure pipe of the three sets of hydraulic pumps is brought from near Lake Tahoe, in the Sierra Nevada Mountains. The distance is about thirty miles, and the greater part of the way the water flows through iron pipes, which at one point cross a depression 1,720 feet in depth. The pressure pipe takes this water from a tank situated on the eastern slope of Mount Davidson, 3,500 feet west of the shaft. At the tank this pipe is twelve inches in diameter, but is only eight inches where it enters the top of the shaft. The tank whence the water is taken is 426 feet higher than the top of the shaft, therefore the vertical pressure upon the hydraulic pump at the 3,000 foot level is 3,426 feet. The pressure pipe is of ordinary galvanized iron where it receives the water at the tank, but gradually grows thicker and stronger, and at the 3,000 level it is constructed of cast iron, and is 2? inches in thickness. The pressure at this point is 1,500 pounds to the square inch.
In the early days of hydraulic mining in California the miners thought that with a vertical pressure of 300 feet they could almost tear the world to pieces, and not a man among them could have been made to believe that any pipe could be constructed that would withstand a vertical pressure of 1,000 feet; but we now see that