joint, so that at pleasure, by dropping the pipe, the machinery could be run at various speeds, or entirely stopped.  At the end of this discharge-pipe was a cast tapered nozzle, about 31/2 inches in diameter, in which was inserted a ring of saw-plate steel having the desired diameter, and which was held in place by an annular screw-cap.  By changing the ring, which only required a few moments’ time, any desired amount of water, up to 3 or 4 cubic feet a second, could be discharged against the wheel.  The stop-gate was left wide open while the machinery was running.  The pumping was done by eighteen pumps, of Cornish pattern; the largest amount of water pumped from any one shaft was something over 30 cubic feet a minute; the power at hand, however, was ample to pump more than twice that quantity.  It was rather curious at, this shaft to see more water coming from the pumps than was used on the wheel.  The two diamond drills were driven by a small hurdy-gurdy set on the rear of the drill carriage.  This, but at another tunnel, was afterward modified by placing a separate hurdy-gurdy on a sleeve on each drill-rod; the advance movement of the drill being given by hydrostatic pressure on an annular piston, thus doing away with all gearing.  These eight sets of machinery were run for nearly 21/2 years’ time; the only break being that of a spur-wheel, doubtless caused by the careless dropping of a steel bar between it and its pinion.  Aside from this accident, practically not a dollar was spent for repairs, and the machinery, including the pipe, was in about as good order when the tunnel was finished as when it was first erected.  One man, on a twelve hour shift, operated the machinery at each shaft, besides dumping the cars; two men kept the 18 pumps on the line in order, the principal work being in keeping the suction-pipes for the down-grade headings tight; thus a force of 18 men was only required for the eight shafts.  The cost of the pipe, gates, etc., when put in place, was $14,631, and of the machinery about $60,000.

[Illustration:  FIG. 14.]

At the Idaho gold quartz mine, situated near Grass Valley, California, water-power has been introduced during the past year (1883), taking the place of steam.  The supply main is of wrought-iron, 22 inches in diameter, 8,764 feet long, buried in the ground below frost-line.  The joints, as a rule, are riveted together, with occasional lead joints to admit of slight movements in the pipe.[4] The pipe was coated by placing each joint in a bath of boiling tar and asphaltum; to insure the most thorough coating, it is necessary to keep the pipe for ten or fifteen minutes in the boiling mixture.  A cast-iron stop-gate is placed at the lower end of the main, and also one at each of the branches.  Cast-iron man-holes are attached to the main, which, although they have given no trouble in this particular case, are very objectionable for high pressures, as it is difficult to avoid ruptures with cast and wrought-iron combined, owing to the great difference in the elasticity of the two metals.  The long seams of this pipe are double-riveted, and the round seams single riveted; at the lower end, iron of No. 6 gauge is used.  From the end of the main, the water is led to the several wheels by branches of smaller diameter.