POWER DEVELOPMENT AT NIAGARA. 615 



which will be passed into an alternating-current motor driving a 

 direct-current, low-voltage generator furnishing at last the de- 

 sired electrolyzing current. It has seemed best to submit to this 

 complication of apparatus in order to gain the advantage of en- 

 tire uniformity and interchangeability of power units in the gen- 

 erating plant. Of course, if the power company were to put in a 

 direct-current dynamo for the benefit of the Reduction Company, 

 all that would be necessary would be to send the current over a 

 wire straight to its work ; and it seems remarkable, in view of the 

 thousands of horse power required, that the extra expense of a 

 motor and dynamo to transform this quantity appears preferable. 

 The electrical yjower unit which has been decided on after the 

 most exhaustive, and presumably competent, expert examination 

 of the requirements of the situation, will be of a capacity for con- 

 tinuous work of five thousand electrical horse power (or three 

 thousand seven hundred kilowatts), and will be directly connect- 

 ed with a pair of turbines of similar power. All the generators 

 will be mechanically identical in construction and have parts in- 

 terchangeable with each other. The advantage of this, besides 

 the obvious one of having a single set of spare parts suffice 

 against the breakdown of any machine in the station, is that, 

 from a point of view of the electrical aspect of the case, of the 

 machines being able all to be put in parallel, as it is called. The 

 expression may not be a familiar one to some of our readers, and 

 the following hydraulic analogy may be of service in leading to 

 an understanding of what is meant by it. Let us assume that we 

 have several pumping engines of equal power, and that we are 

 using them all to pump water from one reservoir into another at a 

 higher level. Obviously the total amount of water pumped will 

 be what a single machine handles multiplied by the number of 

 them. Had, say, one of the pumps been weaker than the others 

 had it, that is, not been strong enough to force water up to the 

 height that the others did the result would be that, instead of 

 doing any work when put, as we may say, in parallel with the 

 others, it would have been unable to withstand the head, and 

 water would have forced itself back through it into the lower 

 reservoir. The same way with dynamos, or generators as they 

 are usually called when referring to the machinery in a power as 

 distinct from a lighting station. The advantage of working in par- 

 allel is, that if we have, say, six machines all "pumping" current 

 into the same mains and one breaks down, we may take it out of 

 circuit, and, by temporarily overloading the other five, which can 

 always be done for a short time with good machines, keep on sup- 

 plying full current to consumers. Should the power company 

 have decided to put in a special machine for aluminum, and other 

 special ones for other local work, and still more for distant work. 



