XXX. W. H. WARREN. 
generators by means of vertical shafts. The turbines were made 
by Messrs. Faisch of Switzerland. The electrical generators are 
of the Tesla polyphase alternating current type. Each generator 
delivers an alternating current to each of two circuits, the currents 
in these circuits differing from each other in their time relation 
or phase by 90°, that is to say, the current delivered to each 
circuit attains its maximum value at the instant when the 
current delivered to the other circuit is zero. ‘The frequency is 
twenty-five cycles per second, in other words the current is 
reversed 3,000 times per minute. By means of rheostats con- 
trolling the field circuits of the generators the potential of the 
current delivered is adjusted up to the limit 2,400 volts. 
The currents delivered by the generators are conveyed through 
heavily insulated cables to the switch board, there by means of 
suitable switching devices the engineer in charge can connect any 
one of the generators, or any combination of them to the external 
_ circuits which convey the current from the power house to the 
consumers, Currents intended for transmission to considerable 
distances, as for example to Buffalo, will pass from the switch- 
board through similar lead covered cables in the power house 
subway and the bridge to the transformer house. ‘There it is 
proposed to transform the current up to 20,000 volts. At the 
distant end of the circuit stepdown transformers will be used to 
reduce the potential to an amount suitable for local requirements. 
In the case of large motors used in Niagara, the current will 
be probably supplied at the voltage delivered by the machines 
without transformers, but for smaller motors and where direct 
currents are required stepdown transformers must be used. The 
‘Niagara generators represent the highest state of the art of 
design and construction of electrical machinery. The revolving 
parts consist of the vertical axis of the turbine shafts, which are 
twelve inches in diameter ; the armature is stationary, but the 
field ring carrying the field magnets is suspended from the top of 
the vertical shafts and revolves with it. The field ring is made 
of nickel steel of very high quality, having a tensile strength e 
