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THE POPULAR SCIENCE MONTHLY. 



fully of the possibility of distributing 

 the electric light from house to house ; 

 but to-day the problem does not present 

 any greater practical difficulty than the 

 distribution of water or gas. "When Sir 

 Humphry Davy first made an exhibition 

 of the arc light he used for tbe purpose 

 a battery of two thousand voltaic cells. 

 Light so produced could never have 

 come into general use on account of the 

 excessive cost. Faraday had to formu- 

 late the laws of induction, and the dy- 

 namo had to be developed, before Davy's 

 discovery could be turned to practical 

 account, and even then a vast amount 

 of ingenuity had to be expended in the 

 arrangement of details. The incandes- 

 cent light was a later development. An 

 incandescent lamp is a simple thing to 

 look at, but only those who have studied 

 the subject know how much of laborious 

 experiment and research it took to bring 

 it to its present condition of perfection. 

 The dynamo which, practically speak- 

 ing, gives us the electric light, gives us 

 also electric traction and electric power 

 generally. "We are only beginning to 

 realize the advantages which our new- 

 found force may have in store for us in 

 this direction. Every month the electric 

 street car is more and more displacing 

 the horse car, with added comfort to 

 passengers and diminished wear of our 

 thoroughfares. Power is conveyed si- 

 lently over wires from central stations 

 and distributed wherever it may be re- 

 quired for manufacturing purposes, sav- 

 ing a vast outlay in separate boilers and 

 engines, and greatly economizing space. 

 In great telegraph centers the dynamo 

 is displacing cell batteries for the pro- 

 duction of current. It is also used for 

 electrolytic operations on a large scale. 

 Nothing, perhaps, is more impressive 

 than to witness the operation at the 

 same moment and on the same spot of 

 three distinct forms of force, mechani- 

 cal or physical, electrical and chemical, 

 one merging into the other. The water- 

 wheel or the steam-engine furnishes 

 mechanical power ; the dynamo, taking 



up that power, converts it into electri- 

 cal energy, which again, conducted to an 

 electrolytic cell, is further changed into 

 chemical action. Nothing could more 

 powerfully bring home the lesson that, 

 in the last analysis, all energy is one. 

 "Vast industries would disappear from 

 the earth if the various applications ot 

 electrolysis could by any means be lost 

 electro- plating, electrotyping, electro- 

 metallurgy, and a hundred other special 

 applications of electro-chemistry. It 

 takes a considerable effort of thought 

 and memory to realize the extent to the 

 every - day operations of the modern 

 world are dependent upon a power 

 which but a few generations ago was a 

 matter of more or less crude specula- 

 tion and idle wonder. In electro-weld- 

 ing we have a process, strictly speaking, 

 analogous to the production of the elec- 

 tric light; the energy of electricity is 

 converted into heat at a given point 

 with the most marvelous results. The 

 new science is stretching forth its hands 

 in every direction, and its achievements 

 to-day are but an earnest of what it is des- 

 tined to accomplish in the near future. 



There is, however, another aspect of 

 the matter which is deserving of atten- 

 tion. From having been, up to a short 

 time ago, a subject concerning which 

 the most vague and confused ideas were 

 generally entertained, electricity is now 

 furnishing matter for the formation of 

 one of the most exact sciences. It is 

 true there is a vast amount of popular 

 ignorance respecting it still ; one might 

 not, perhaps, have far to go to find 

 " educated " people who imagine that 

 Edison and electricity are almost con- 

 vertible terms, or at least that electricity 

 was fished bodily out of the depths of 

 the unknown by Edison ; nevertheless, 

 the light is spreading, and the very op- 

 erations which the applications of elec- 

 tricity involve are furnishing a valuable 

 education to a large section of the com- 

 munity. Electricity is above all things 

 measurable, and measurable in a great 

 variety of ways ; and the measurement 



