ELECTRIC LIGHTING, PROGRESS OF. 



273 



this country propose to carry out, using for 

 this purpose the storage-battery devised by Mr. 

 Brush, and the Swan incandescent lump, as in- 

 dicated above. By means of an automatic de- 

 vice, the batteries are placed in circuit when 

 the electro-motive force falls below a certain 

 point, and cut out again as soon as sufficiently 

 charged. Combined with this is a register- 

 ing instrument, which indicates upon a dial 

 the current supplied to the battery. The street- 

 wires, for the distance which they enter a 

 house to make connection with the battery, 

 will be thoroughly insulated, and so placed that 

 they can not be handled, so that the danger 

 apprehended from allowing conductors bear- 

 ing powerful high-tension currents may be 

 thoroughly provided against. The Brush-Swan 

 Company expects to begin putting its system 

 into operation in the course of a few months, 

 and its progress will be watched with great 

 interest, as having an important bearing 

 upon the character of future electric instal- 

 lations. 



The other considerable arc-electric lighting 

 company in this country, the " United States," 

 is also proposing to adopt the storage-battery 

 system of incandescent lighting. This com- 

 pany controls the Maxim incandescent lamp, 

 which is being quite largely introduced at vari- 

 ous points. In New York no considerable 

 plant has yet been established, but the light is 

 being supplied, to a limited extent, from the 

 arc-lamp stations. It may be remarked here 

 that the Weston arc-lamp, which is furnished 

 by this company, differs from the other arc- 

 lamps now on the market, in using a cur- 

 rent of much lower electro-motive force, and 

 nearly twice the volume. The arc is exceed- 

 ingly short, being not more than one thirty- 

 second of an inch, while that of the Brush is 

 one sixteenth, and the Fuller three sixteenths 

 of an inch. The light of the Weston, on this 

 account, is free from the violet rays noticeable 

 in lamps of longer arc, and is, therefore, more 

 agreeable. The use of a current of such vol- 

 ume requires larger conductors than are neces- 

 rary with a smaller current, and it can not, 

 therefore, be operated upon long circuits as 

 economically as those of higher electro-motive 

 force. 



Various tests have from time to time been 

 made of both arc and incandescent lamps, as 

 well as machines ; but the first thorough and 

 complete examination is that made on the ap- 

 paratus shown at the Paris Exhibition of 1881. 

 Including, as these did, all the chief Lamps 

 and machines now before the public, the re- 

 ports, in which these tests are embodied, are 

 comprehensive and authoritative statements of 

 the commercial value of the present electric- 

 lighting apparatus. 



The main committee consisted of MM. Allard, 

 Joubert, T. Le Blanc, Pettier, and H. Tresca. 

 The results obtained by these experts were 

 communicated to the " Academie des Sciences " 

 in four papers bearing the titles : 

 VOL. xxii. 18 A 



1. Continuous-current machines and regu- 

 lators. 



2. Alternating- current machines. 



3. Electric candles. 



4. Incandescent lamps. 



Besides this committee, a sub- committee was 

 appointed, specially charged with the exami- 

 nation of incandescent lamps. As the report 

 of this latter committee on incandescent lamps 

 is much fuller than that of the chief one, it is 

 alone reproduced here, and the report of the 

 main committee confined to the first three of 

 the above items. 



The unit of power adopted by the committee 

 is the cheml-vapeur, which is equal to 75 kilo- 

 grammetres, or 542J foot-pounds per second. 

 This is slightly less than the English horse- 

 power, which is 550 foot-pounds per second. 



The luminous intensity is expressed in carcels 

 equal to 9^ standard candles and the results 

 of the measurements in various directions are 

 averaged so as to make the intensity the same 

 in every direction, that is, at every point on the 

 surface of a sphere of which the arc is the cen- 

 ter. Even when measured in the best direction 

 the results obtained by the committee are much 

 under those stated by the various manufactur- 

 ers, while the average spherical intensity is very 

 much less. The table on page 274 gives the 

 results with continuous-current machines and 

 regulator lamps. 



An examination of this table shows that ma- 

 chines transform on an average 85 per cent of 

 the work expended on them into electrical 

 energy, and of this electrical energy from 50 to 

 77 per cent appears in the arc, and that for 

 each horse-power of energy expended in the 

 arc there are obtained 



120 carcels, in lights of SCO to 1,000 carcels. 

 100 " " "250 



71 " " " 40 " 



The experiments upon alternating-current 

 machines and lamps were made with the ma- 

 chines of De Meritens and Siemens, and with 

 the Serrin, Berjot and Siemens lamps. In one 

 case a Serrin light-house lamp was operated by 

 a De Meritens machine, giving a light the 

 mean spherical intensity of which was equal to 

 931 carcels, with an expenditure of mechanical 

 power of 11 '7 horse-power. This was equiva- 

 lent to 79'6 carcels per mechanical horse-power, 

 while but GO carcels were obtained with lights 

 of the same power operated with continuous 

 currents. The superiority of the alternating 

 current shown in this particular case was not, 

 however, maintained in lights of lower candle- 

 power, as the result fell to 59 '7 carcels in the 

 Berjot lamps of 150 carcels (arranged in a 

 series of five), and to 33 '3 carcels in the Sie- 

 mens differential lamps of 39 carcels (12 in 

 three circuits). 



The candles examined were those of Debrun, 

 Jablochkoff, and Jamin. The Jablochkoff can- 

 dle showed from 46 to 51 carcels per arc horse- 

 power, and from 31 to 35 carcels per mechanical 

 horse-power, while that of Debrun, the experi- 



