738 POPULAR SCIENCE MONTHLY. 



fore has to be reduced by being passed through the machines shown 

 in the illustration, which are called step-down transformers, their 

 office being to reduce the pressure of the current. These trans- 

 formers in reality do not reduce the pressure of the current; what 

 they do is to generate a second current, by the aid of the energy de- 

 rived from the first, of a much lower pressure. The power of the 

 substation is to be used for all purposes, for " arc " and incandescent 

 lighting, fqj driving stationary motors, and for the operation of elec- 

 tric railways. 



The Big Cottonwood Power Company has about completed 

 the construction of an important plant to utilize the water power of 

 the lakes in the Wahsatch Mountains, and distribute it in and around 

 the vicinity of Salt Lake City. These lakes, which empty into the 

 Big Cottonwood Canon, lie at elevations above the sea ranging 

 between eleven thousand and thirteen thousand feet; therefore the 

 total amount of power available is very large on account of the enor- 

 mous fall. The Big Cottonwood Company controls a fall of about 

 one thousand feet, but in the present installation will only use about 

 four hundred feet. The water is confined in a reservoir, as shown in 

 the topographical map on page 737, and is conveyed by pipe line to 

 the power house, as is shown quite clearly in the illustration of the 

 site of the latter on page 739, where the pipe is seen in the back- 

 ground, descending between the mountains. To guard against an 

 accidental giving way of the reservoir, as well as to render it possible 

 to empty it when desired without interfering with the operation of 

 the plant, the pipe line is carried along the bottom to the upper end 

 of the reservoir, where it connects with the main source of supply. 

 By closing one gate and opening another, the water may be drawn 

 from either point, as occasion may require. 



The capacity of this plant is about twenty-five hundred horse 

 power, which will be distributed at a distance of about fourteen 

 miles. The water wheels are mounted directly upon the shafts of the 

 electric generators, as can be seen from the illustration of the in- 

 terior of the power station shown on page 741. The generator in 

 the foreground is not provided with a water wheel; the only part 

 of this apparatus visible is the water pipe under the shaft, between 

 the two bearings. This generator was not completely mounted 

 when the photograph was taken, but the two machines in the back- 

 ground, it will be noticed, are provided with water wheels, which 

 are mounted on the shaft in the space between the two bearings, 

 which in the front generator is uncovered. The simplicity and 

 solidity of this apparatus are very striking, and, being one of the 

 latest installations, show clearly the perfection to which machinery 

 of this class has been carried ; and from the fact that the capacity of 



