The “sump” is the well or hole sunk below the bottom of a shaft, for the purpose of holding the water flowing in from above. In this is placed the “suction” of the pump, and into it is collected the water from all parts of the mine. Although “sump” is now considered an English word, it was doubtless derived from the German word, “sumpf,” which means a marsh, pool, bog, or fen. When miners fall down a shaft it is frequently necessary to fish their mangled remains out of the sump with grappling irons.
As some persons may desire to know how sinking can be carried on in the bottom of a shaft where there is a strong influx of water, it may be well to explain the matter. On the end of the pump-column or tube which comes down near to the bottom of the shaft, is a piece of flexible hose, the same as the “suction” of a fire-engine, and this is moved about from side to side in the shaft, always keeping the end of it in the low places where the water collects.
CHAPTER XLIII.
CURIOSITIES OF VENTILATION.
The only air-shaft on the Comstock lode worthy of the name, is that of the Belcher Mining Company. In many situations air-shafts do not seem to be required, connections with the main working shafts of other mines serving the same purpose. In some places along the lode are old shafts—sunk in the early days—with which connection has been made, and these often do very good service as air-shafts. The air-shaft of the Belcher Company is sunk at a point about 100 yards to the northward of their main hoisting-works.
The size of the excavation made in the rock is 8×14 feet. This, when timbered up, gives two compartments, each 6×6 in size. Where the rock is hard and perfectly solid the shaft is cribbed with timbers 6×12 inches in size; but where it is soft and inclined to swell, it is timbered in sets; timbers 12 inches square being used. All of this work is done in the most substantial manner possible. From the surface to the 1000-foot level the shaft is carried down vertically, but from this point it is on an incline corresponding to the dip of the ledge, which is about 36 degrees, and to the east. The portion of the shaft which is carried down on an incline was kept in the west country rock lying back of the ledge. The object in keeping in this rock was to avoid ground that would be liable to swell and then crush in the sides of the shaft.
This shaft is of the same size and is constructed after the same plan as that destroyed by fire, October 30, 1874, by which accident a large number of men were badly burned, and some lost their lives. It extends down to the lowest levels of the mine and will be continued downward as new levels are opened. In excavating the shaft, work was begun at the same time on the surface and down at the 850-foot level of the mine—the men below digging upward while those above were sinking.
The shaft is “downcast,” that is, the air from the surface of the earth is drawn or sucked down into it and finds its way out through the main working shaft and other shafts connecting with the mine by means of drifts. The first shaft was also a “downcast,” but when on fire, the draught was changed, and a column of flame darted upward from its mouth a hundred feet into the air, with a roar that could be heard at the distance of a mile or more. Had not the shaft caved and filled up with rock after the timbers were burned out of it, it would always have remained an “upcast;” at least, so say all the old miners.
Here it may not be out of place to speak of some of the curiosities of ventilation.
The Yellow-Jacket shaft, previous to the great fire in that mine some years ago, had a strong draught downward; the fire changed the draught, and it has ever since remained an “upcast.” This is a curious freak of nature which all old miners have observed. When once the change in the draught takes place it is permanent. A curious thing in ventilation—and it is a nut for the scientists to crack—is that everywhere along the Comstock lode the tendency of all currents of air is to the southward—in the same direction that the ore chimneys tend. Here certainly is at work another mysterious force of nature. This tendency of the air-currents to move southward has never been overcome, except in one or two instances, and these exceptional cases will presently be mentioned. There are some queer courses taken by currents of air when once they have descended beneath the surface of the earth, which none of our scientific men have attempted to explain. The commonly accepted theory is that when two shafts are connected by means of a drift, the draught or ascending current of air will be through the higher shaft—the longer branch of the siphon—but exactly the reverse is seen if the short shaft happens to stand to the southward of the long one.