THE COMBINATION SHAFT.
Of these shafts, that which attained the greatest vertical depth was the Combination—the joint shaft of the Chollar, Hale & Norcross, and Savage Companies. Before work on it was discontinued it had reached the great depth of 3,250 feet. There is but one deeper vertical shaft in the world. This is the Adalbert Shaft, in the silver mines of Bohemia, which is 3,280 feet deep. There is no record of the time when work on this mine in Bohemia was commenced, though its written history extends back to 1527. The Combination Shaft was sunk at the rate of three feet a day, even in rock as hard as flint. The whole shaft is sunk in very hard rock (andesite), every foot of which had to be blasted. It is thirty feet by ten feet in size and is divided into four compartments for the accommodation of the hoisting and pumping apparatus.
The shaft was sunk to the depth of 2,200 feet before more water was encountered than could be hoisted out in the “skips” with the dirt. Down to the 2,400 level two Cornish pumps were used, each with columns fifteen inches in diameter. A drift run west into the vein tapped more water than the Cornish pumps could handle, when the management introduced hydraulic pumps. These pumps are run by the pressure of water from the surface through a pipe running down from the top of the shaft, whereas the Cornish pumps were run by huge steam engines. The shaft is connected with the Sutro drain tunnel at the depth of 1,600 feet, and to that point it was necessary to pump all the water. At the 3,000 level were placed a pair of hydraulic pumps, the deepest in the world. In Europe the deepest point at which a hydraulic pump has ever been worked is 2,700 feet. This is in the Hartz Mountains, in Germany.
When one stood at the 3,000 level and looked up a compartment of the shaft (five feet by six feet in size) the little spot of daylight seen at the top appeared to be about four inches square. At this great depth even the smallest bit of rock falling from the top whistles like a rifle-ball before reaching the bottom, and, striking a man on the head, would instantly kill him. Should a man fall that distance little would remain on which to hold an inquest—his body would be quite “dissipated.” The Cornish and the hydraulic pumps working together had a daily capacity of 5,200,000 gallons—a small river! Hydraulic pumps were placed at the 2,400-foot level, the 2,600 and the 3,000 levels. Some idea of the great size of these engines and pumps may be formed when it is stated that the stations excavated for them were eighty-five feet long, twenty-eight feet wide, and twelve feet high. All this space was so filled with machinery that there was only room left to move about among it. Drifts were run to the west to the lode at the 2,400, 2,800 and 3,000-foot levels. On the 3,000 level the distance from the shaft to the east wall of the vein was found to be only 250 feet. The lode at this depth (3,000 feet) was found to be of great width and well mineralized—indeed the Hale & Norcross folks had a good showing of ore.