pendently, as they do, they will not necessarily commence and finish their strokes at the same time. But, in order to discuss the system under its extreme conditions, I will consider the two pumps as working together, thereby making the velocity of the supply water and the inertia of the moving masses a maximum. Therefore, in each pump, let 0, 0, and 0, 0, see detail drawing, be the four pressure cylinders, and T and Tthe pump cylinders for raising the drain water to the Sutro Tunnel. Let V and V be the valves leading to the pressure cylinders from the supply and return pipes, and let the plungers be connected with a crosshead (as shown in drawing), so that when any movement of the plunger, O O, takes place, the plunger, T T, will be carried along also. Now, let us follow the operation of these pumps, first assuming, however, that the pressure of the water in the supply pipe is great enough to produce motion of the plungers, 0, 0. First, suppose the valves, V, to be opened (valves, V, remaining closed). The two plungers, 0 0, will be forced over to the right, carrying with them the larger plunger, T Î. While T travels to the right, the space left by it is immediately filled with drain water coming through the suction pipe, W. Now, suppose valves, V, be closed and the stroke finished, the valves, V, are then opened, and the pressure of the supply water against the plungers, O, forces them to the left, and the water remaining in cylinders, O, is forced through the valves, V, into the return pipe, and thence into reservoir, N, upon the surface. At the same time, the water which was drawn into cylinder, T, on preceding stroke, is now forced (on account of the check valve, C, closing) through D into discharge column, D, and thence 800 feet into the Sutro Tunnel. Again, while this stroke to the left is being made, the space left by plunger, T, is being filled with drain water through suction pipe, W. At the completion of this stroke, valves, V, are closed and valves, V, are opened, the crosshead and plungers again move to the right, and the waters remaining in the cylinders, O, is again forced through return column into reservoir, N. At the same time, the water in cylinder, T, is forced upward (on account of check valve, C, being closed) through D into D, and thence to Sutro Tunnel. When crosshead, and plungers are again over to the extreme right, valves, V, are closed and valves, V, opened, and thus the operation continues, the valves, V and V, being worked automatically by means of tappets carried by the crosshead. The number of strokes made by these pumps evidently depends upon the pressure of water in the supply pipe, and also upon the rapidity with which the valves, V and V, are opened and closed. In the preceding, I have followed the action of but one underground pump, but, as I have said before, the two are alike in every respect, and both draw their water from and discharge it into the same columns. From the above remarks, it will be seen that the sole object of these two underground pumps is to raise the drain water from the 2,400 level of the mine to the Sutro Tunnel, a distance of 800 feet. The object of the accumulator, A, upon the surface, is to accumulate the water within it, under a pressure great enough to work the pumps, P, and the object of the compound steam engine and pumps, T (on the surface), is to supply the accumulator with exactly the same amount of water taken from it, to run underground pumps. Furthermore, it will be noticed that the same amount of water which is used to run these pumps, P, is returned to reservoir on the surface, from whence it is forced into the accumulator by pumps, T, to be used over and over again. Right here it might be well to mention the fact, that the surface pumps, T, were constructed with a capacity great enough for two more pumping engines, similar to those just described (P), so that when a depth of 1,000 feet more was reached, this extra set of pumps would be put in at the 3,400 level, and the process go on as before. ¡ The above description, by Mr. Moore, explains the action of the hydraulic pumps on the Comstock. Since it was written the pumps have been running several years, and the springs (marked S on the diagram) have been replaced by air chambers, so that the concussion of water lost in discharge, pressure, and return columns, has been overcome by means of air chambers erected on the same station with the pumps. It was found impossible to properly regulate the springs to work as efficiently as the air chambers have done. The population of Virginia City decreased so rapidly that the water company were enabled to supply the Combination Shaft with water to run their pumps. Instead of the accumulator and surface engine being required, they were only kept as a reserve in case of a failure of the water supply. After the shaft had been sunk considerably in depth, two more pumps were added on the 2,600-foot level, and later on two extra additional ones at the 3,000-foot level, which raised 4,000,000 gallons of water daily to the Sutro Tunnel, a direct lift of 2,400 feet of hot water, at a temperature of 140 degrees. In all there were six pumps, which have been running constantly, without a single stop, this last number of years. It is only in October last that they were shut down, by order from the companies, because deep prospecting was found unprofitable. They are now submerged in several hundred feet of water. The Risdon Iron Works have built several other pumps on this same style, and all have worked successfully. These pumps have lately been introduced in England, at some large collieries there, and are also working satisfactorily. WEIGHT OF QUARTZ MILLS. As many miners have no information of the details of weight of the parts of quartz mills, the following statement concerning five, ten, and twenty-stamp gold mills has been obtained from the Joshua Hendy Machine Works, San Francisco. Of course the weights of the ore-feeders and the concentrators depend upon the pattern used, but the figures given will afford a basis upon which miners can estimate what freights have to be paid. Rock-breaker. MEMORANDA OF WEIGHTS OF FIVE-STAMP QUARTZ MILL (Gold). Ore feeder ("Challenge") 4,500 lbs. 750 lbs. 4,000 lbs. 500 lbs. 550 lbs. 1,700 lbs. Bossheads, 200 lbs. each, five 1,000 lbs. Tappets, 100 lbs. each, five 500 lbs. Cams, 150 lbs. each, five 750 lbs. Cam shaft. 350 lbs. Rock-breaker. MEMORANDA OF WEIGHTS OF TWENTY-STAMP GOLD QUARTZ MILL. Ore-feeder ("Challenge"), 750 lbs. each, four. The Pacific Iron Works of San Francisco also furnish data to this report on both silver and gold mills, as follows: TEN-STAMP FREE ORE SILVER MILL. One 4 feet by 12 feet grizzly. One 10-stamp battery, 750 to 800 pound stamps. One 3-foot clean-up pan. One amalgam safe and strainer. One quicksilver elevator, with tanks, pipes, etc. Two traveling crabs for battery and pans. One 14-inch silver retort. One melting furnace. Shafting, pulleys, boxes, etc., for mill. Belting for mill. Pipes and fittings complete. One Duncan concentrator for saving quicksilver and amalgam. Weight of the above, 87,000 pounds. Power required: One 50-horse power engine. One 50-horse power boiler. One 50-horse power feed-water heater. One No. 3 steam pump. Steam and water connections. Weight of the above, 24,500 pounds. Total weight of the above, 111,500 pounds. TWENTY-STAMP FREE ORE SILVER MILL. One 4 feet by 12 feet grizzly. One 8 by 10 Blake crusher. Four automatic ore feeders. Two 10-stamp batteries. Eight 5-foot combination pans. Four 8-foot settlers. One 4-foot clean-up pan. One quicksilver elevator, with tanks, pipes, etc. Three traveling crabs and track for batteries and pans. Two amalgam safes and strainers. Two 14-inch silver retorts. One melting furnace. Shafting, pulleys, boxes, etc., for entire mill. Belting for entire mill. Pipes and fittings for mill. One Duncan concentrator, for saving amalgam and quicksilver. Weight of the above, 180,000 pounds. Power required: One 100-horse power engine. Two 50-horse power boilers. One 80-horse power feed water heater. |