and Surfaces of Incandescence Lamps. 379 
Professors Ayrton and Perry have drawn attention * to a 
connection between the candle- power of a lamp and the working 
potential, and they find that in very many cases the cube root 
of the candle-power is proportional to the working potential 
minus a constant. Now, this is equivalent to saying that the 
candle-power of the lamp is proportional to the cube of the 
potential measured above a certain point. 
I have examined some records of measurements of Edison 
lamps to put this law to further test, and the results are 
given below for two 16-candle Edison lamps measured by 
myself, and one 8-candle lamp measured by Prof. Jamieson. 
Edison 16-candle Lamp.—No. 1. 
| ees oss 
Candle- Volts, a : v5 17. | 
Tis isi ee AAR WOR CEL (Pa Mia 
22,. ited ae <= incerta es | eee) 
16 105:27 2-5726 48-10 18:8 
| 1S 99:56 2-2572 49-39 188 | 
| 8:25 9432 2-0206 37°15 184 | 
| 48 90-08 1-6869 32-86 19 | 
Pee | 85°74 1-4095 28°57 20 | 
[2 | 8122 * | 12599 2405 | 1908 | 
Hdison 16-candle Lamp.—No. 2. 
| S ‘Wy a | v—50. 
< . Vv. 4 | U—vJU. 3/T 
pee | | | = sonata 
mses: «=| zis |. see. |. als | 
13 10003 «| «623518 | «S50 Reicha 
95 Baty thie 1G cote e's ARGS ie ee 
8:25 9479 | 2019 | 44-79 22: Alea 
Lee o7eg | 2 Fog | 4989 | 288 
es: 8812 | 1765 | S812 | 222 | 
| | 
Hdison 8-candle Lamp used by Professor Jamieson. 
Edt ii v—28°7. 
K. | v. v—28°7. | 4/ K. OK, 
52 459 17-2 | 1-7324 9-928 
oo. | 46°7 18 | 18371 9798 
8:2 48°3 19-6 20165 9-720 
1 ae 519 23°2 2°3453 9-892 
143 | 53 24°3 | 2446 9°937 
mae! 56-2 27°5 2772 9-921 
253 | 58 29°3 2936 | 9981 
308 61-1 324 3°296 9°851 
ao. | 63°71 3b4°4 3°525 9°759 
| | 
* “Qn the most Economical Potential-Ditference to Employ with 
Incandescent Lamps: ” ‘The Electrician,’ March 7, 1885, p. 348. 
