From the end of the main, the water is led to the several wheels by branches of smaller diameter.

The water is delivered at the hoisting-wheel with a total head of 542.6 feet. For power and for mill uses, etc., the required supply is about 8 cubic feet a second; this draught reduces the effective head to say 523 feet.

The work done consists in driving the following described machinery:

A large air-compressor - 2 cylinders, double acting, air compressed to 75 pounds - requiring about 140 horse-power.

A line of Cornish pumps, forcing the water from a depth of 1,450 feet vertical; 12-inch plungers for upper 800 feet, 6-inch plungers for lower 650 feet, with 6-foot stroke, requiring from 55 to 70 horse-power.

Hoisting from a double-compartment shaft - two connected winding reels, moving separate cages - requiring 35 horse-power, or more.

A few small machine-tools and smithy forges, requiring 3 or 4 horse-power.

A 35-stamp mill, with concentrating apparatus, etc., requiring about 70 horse-power.

The total amount of power required being say 320 horse-power, for which seven Pelton hurdy-gurdy wheels are employed.

The power in all cases is transmitted by systems of Manila rope belting; the rope is 2 inches in diameter; the grooves in the sheaves or pulleys are slightly oval, so that the rope does not go quite to the bottom; the ropes are horizontal, and run very slack (no tighteners), with no appreciable slip; the splices are made very long, to obtain uniformity in diameter.

FIG. 15.

This method of transmitting power appears to work most perfectly and has given excellent satisfaction. It is thought, at the Idaho, to be greatly preferable to the gearing formerly in use when the works were driven by steam (for such work as pumping or hoisting, leather or rubber belting is never used), besides being much cheaper in first cost.

The wheel driving the air-compressor is 6 feet in diameter, running 300 turns[5] per minute, with 1-15/18-inch nozzle; three ropes are used from the wheel shaft to the counter-shaft, and six ropes from the latter to the fly-wheel shaft.

For driving the pumps, there are two water-wheels, set on the same shaft, one 5 feet and the other 7 feet in diameter, either of which can be used at will, thus permitting different rates of speed; two nozzles are placed on each wheel, so that if necessary the power can at any time be doubled. The smaller wheel has a 1¼ inch nozzle, and runs 360 turns a minute; the larger has 1⅛-inch nozzle, and makes 270 turns a minute. There are two ropes from the wheel-shaft to a counter-shaft, and four ropes to the fly-wheel shaft, on which is the pinion driving the spur-wheel attached to the pitman of the pump-bob. Hoisting is done by two wheels placed side by side on the same shaft, the buckets and nozzle of each wheel being placed in opposite directions. Both wheels are 8 feet in diameter, with 15/16-inch nozzles, and make at full speed about 225 turns a minute. Reversing the movement of the shaft is done by shutting off water from one wheel, and turning water on the other wheel; the two water-gates for these nozzles are quickly opened or closed by hydrostatic pressure, afforded from the water main.

In addition to the usual brakes on the winding-reels, a brake is placed on the wheel-shaft, so that it can be stopped in a very short period of time.

The shock to the pipe by the almost instantaneous cutting off the water at these hoisting-wheels (nearly one cubic foot per second) has not apparently had any injurious, effect. To lessen this shock, a compensating balance was designed, but which is not now in use. A wheel, of small diameter, is used for the smithy, etc., running at a very high velocity. The wheel driving the stamp-mill is 6 feet in diameter, makes 300 revolutions a minute, and is supplied through a 1-3/16 inch nozzle. The head of water at this point is a few feet greater than at the other wheels. Power is transmitted from the hoisting and mill-wheel shafts by two and four ropes, the same as with the pumping rig. The amount of work done, or of water used, has not been carefully determined; judging from the indicator cards taken from the old steam-engines, the managers of the Idaho believe that an efficiency of fully 80 per cent. of the theoretic power of the water is obtained on the main driving-shafts of the machinery. The substitution of water for steam-power has resulted in a large saving of expense.

Although the hills near by are covered with fine forests, thus making wood cheap, and although a round price is charged for water by the company furnishing it, the cost of the water is considerably less than that of the wood formerly used as fuel. The cost of attendance is altogether in favor of the water-wheels, which hardly require any attention. The cost of the change from steam to water-power was $46,496.32.

[4]With buried wrought-iron pipe this precaution is unnecessary, as the elasticity of the iron will admit of the movement due to changes of temperature, without injury to the rivets.[5]The revolutions per minute, of these wheels, as here given, are only approximate, as the design was to have the bucket speed=½ 2(gh)½.