120 ELECTRIC LIGHTING. 



will diminish, not in direct proportion, but in progressive pro- 

 portion to the excess of power employed. Thus, if 80 horse- 

 power are required to produce 15,000 units of light at one lamp, 

 and if the light is, by division, reduced to 200 units, 160 horse- 

 power will produce not simply 400 units, but a much larger pro- 

 portion, which will increase, not by addition but by multiplication, 

 in proportion to the excess of power employed. It is, therefore, 

 not impossible to obtain a divided light with a certain intensity, 

 but on condition that the quantity of electricity produced shall 

 be raised to a power much greater than that which will give a 

 single light representing the same number of candles. 



The question is to ascertain the proportion between the two 

 terms, that is to say, whether the amount of power required for 

 useful division be not out of proportion with the result obtained, 

 or in other words, if enormous apparatus would not be required 

 for an inconsiderable effect. This reduces the problem to the 

 total cost of erection and maintenance. The question may be 

 thus stated : If 80 horse-power produces a light of 15,000 candles 

 in a single lamp, how many horse-power would be required to 

 bring up the light to the same value of 15,000 candles when 

 divided among several lamps ? 



Edison is seeking for the solution of this problem, which it 

 would seem he has not yet found. This is the one important 

 question. Edison has also to invent a generator of unheard-of 

 power, and in this he says he is sure of succeeding. But in the 

 meantime he has to try those which are at present in use, in 

 order, no doubt, to find which comes nearest to his ideal, that it 

 may supply the most advantageous data for constructing his own. 



EFFECTS OF THE RESISTANCE OF EXTERNAL CIRCUITS. 



If we were to take into consideration only the proper re- 

 sistance of the conductors composing an external circuit, it 

 is evident that the maximum of electric intensity, yielded by 

 the generator, would be obtained when the external circuit 



