An example of a large modern trans mission plant is that erected in 1890 for the Schaffhansen Spinning Mills in Switzerland. This example is not only interesting on account of its magnitude, but beam's° it has been planted, so to say, into the very stronghold of rope transmission, namely, at the Falls of the Rhine, where the last generation of Swiss engineers carried out such admi rable work in teledynamie transmission that the present, generation can only but cannot improve upon it.
spinning mills arc on one side, and the generating station is on the other side of the river, the distance be tween the two hieing about 750 yards. In the generating station there is room for five 350 horse-power turbines, of which four are now in place. hint of these only two are as yet used in connection with the electric power transmission. The power of these turbines is sold to the spinning company at the rate of $13.75 per annual horse-power taken off the rope pulleys. The turbines are horizontal wheels, and their vertical axes are geared by bevel wheels with the rope pulleys, by which motion is conveyed through cotton ropes to the two generating dynamos. The latter are six-pole machines, each designed for an Output of 330 amperes at 624 volts. and in regular work these machines are coupled par-allel. The machines, and, in fact, the whole installation, with the exception'of the hydraulic works, were designed by Mr. C. E. 14 Brown. The generating station contains two 300 horse-power dynamos, which are over compounded, so as to produce a constant pressure of 600 volts at the motor station, the loss in the line being with full current 24 volts. These machines have series wound drum armatures. running at 200 revolutions per minute. Their more important electrical data, as well as those referring to the motors, are given in the following table: A most remarkable example of electric-power transmission is that at the Chollar mine, Virginia City, Nevada. The Nevada Stamp Mill is located near the shaft of the Chollar mine, and is driven by water-power from a reservoir on the side of the mountain, which was not adequate for the full operation of the machinery.
At the 1,050-ft. level of the mine, a subterranean chamber was excavated out of solid porphyry, for the reception of the dynamo-electric generators and water-wheels. This
chamber is 50 ft. in length and 25 ft. in width and 12 ft. in height, clear of all timbers. From the containing the waste surface water, two wrought-iron pipes are led to the subterranean chamber, one 10 and one 8 in. in diameter. At the bottom of the shaft a Y unites these two pipes into a single one, 14 in. in diameter, out of which six 6-in. pipes run to the nozzles of the water-wheels provided to drive the large Brush dynamo-electric generators. The underground electric station is of the most interesting character. The large Brush generators are adapted to the conditions by a few mechanical changes from the standard pattern. They are mounted on a heavy cast-iron base, and are provided with an extended shaft and outer bearing. On each armature shaft and between two bearings a Felton water-wheel is mounted and inclosed in a water-tight cover. The water-wheel is attached to the armature shaft at the place occupied by the pulley, and a coupling is pro vided for detaching the entire end of the shaft carrying tfie wheel from the other end carry ing the armature. (See WATER-WHEELS.) The head of water at this station is 1,650 ft., and the waste is run off through the Sutro tunnel. From each generator the current is led by conductors through the shaft to the surface, where six motors are driven, and the power utilized in supplementing the water wheel at the stamp mill above. The economic value of this arrangement is shown by the following facts: The surface wheel alone requires 312 miner's inches of water to develop power sufficient to drive 40 of the 60 stamps with which the mill is equipped. Moreover, this amount of water is seldom available. Two of the electric motors, working in addition to the surface wheel, will perform the same service with but 72 miner's inches of water, thus effect ing a saving of about 77 per cent., The net commercial of the plant, taking into account all elements of including that in the conducting wires, is about 70 per cent. In other words, 70 per cent. of the power applied to the shafts of the generators in the under ground chamber is delivered for work at the main shaft in the mill.