1 1 8 ELECTRIC LIGHTING. 



d' electricite, tome V., p. 542, the details of these experiments, 

 and I shall here content myself with indicating the results. 



According to these experiments it would follow that the 

 mean work in kilogrammetres per second of the large machine 

 is 576*12, or 7*68 candles, which gives for a light of 100 

 Carcel lamps 0*415 horse-power; for each light per second 

 0*5 1 kilogrammetres. For the small machine this work is 

 210*65 kilogrammetres, or 2*81 horse-power, which gives for 

 a light of 100 lamps 0-92 horse-power, and for one lamp per 

 second 0*69 kilogrammetres. 



" The machines," says Tresca, "worked with regularity for 

 a time sufficiently long to show that there was an absence of 

 all sensible heating. The work expended varied very little 

 during the course of the different series of experiments, 

 although one of the determinations had been made after the 

 machine had been driven for a long time. 



According to the experiments made at Mulhouse by Heil- 

 mann, Ducommun, and Steinlen, who now use this method 

 of lighting, each of their lamps, which supplied a light of 100 

 lamps, required only 1*65 horse-power of mechanical force 

 to be expended. 



Experiments made by Schneider and Heilmann with several 

 machines gave the following results : 



^ , ,. Luminous in- 



Description ;| U1 Work expended tensity measured Remarks on 



of Machine. WF P er in Horse-power. by Bunsen's the Regulators. 



Minute. Photometer. 



( with ground 



Machine B ... 816 1-921 95'6 1 glass globe. 



Machine R ... 816 1*921 122*2 without globe. 



Machine B ... 804 1-980 86 '8 



Machine A ... 810 1*849 85*3 



Machine C .. 763 1-833 103*2 



Machine D ... 883 1*360 687 



These last results are less favourable than those obtained 

 by Tresca ; but we must not lose sight of the fact that he was 

 operating under exceptional conditions, and had perhaps not 

 taken into account the condensed luminous power. From 

 all these experiments, however, the motive power required 



