POWER DEVELOPMENT AT NIAGARA. 621 



details in the design and proposed method of utilizing the current 

 of the generators, we may glance at what has been decided on, 

 and review the more important points raised in connection there- 

 with. 



In the first place, the use of an alternating as opposed to a 

 direct current was decided on, as was to have been expected. The 

 development within the last year or two of alternating-current 

 motors has rendered possible the distribution of electricity for 

 power (as opposed to lighting) purposes over distances before 

 almost out of the question. It has been for a number of years 

 past possible to transmit large quantities of electrical energy for 

 lighting which was not suitable for running the then known 

 motors. The method of electrical distribution for lighting pur- 

 poses that is used in cities is available also for transmission to 

 considerable distances. It consists, as is well known, of a dynamo 

 supplying current at a high voltage to the street lines, and a sys- 

 tem of transformers each taking a portion of this current at high 

 voltage and giving in return a current of greater amperage or 

 volume and of lower voltage for house consumption, the object 

 being simply to avoid loss of voltage or pressure by transmit- 

 ting a heavy current over a light wire. As this may not be 

 quite clear to every reader, it may be as well to say a little more 

 about it. 



The energy of any current is determined by and is equal to 

 the product of two of its properties, its volume or amperage and 

 its pressure or voltage. Letting C represent the amperes and V 

 the voltage, we have that the energy C V. In passing any cur- 

 rent over any wire there is a loss of voltage determined by and 

 equal to the product of two things i. e., the amperage of the cur- 

 rent and the resistance of the wire ; so we have loss of voltage 

 = C R. Now, if we have two currents one, say, of ten amperes 

 and one volt, and the other of one ampere and ten volts the 

 energy will be the same, or ten watts as it is called. If we pass 

 both through a given resistance, R, we shall have a loss of volt- 

 age (= C R) ten times greater in the first than in the second case. 

 But a given loss of voltage amounts to only one tenth as much 

 energy (C V) in the second case with C = one ampere as it does in 

 the first with C = ten amperes, so that with only one tenth the 

 given loss of voltage the energy lost will be only one one-hun- 

 dredth that lost in the first case. What it amounts to is that the 

 loss in passing a given amount of electrical energy through a 

 given resistance is proportional to the square of the current, or 

 amperage, and consequently inversely proportional to the square 

 of the pressure, or voltage. 



If, therefore, current is used in a house at fifty volts and 

 transmitted to the house at one thousand volts, the loss will be 



