376 Dr. J. A. Fleming on the Characteristic Curves 
Hdison 8-candle lamp. 
log R. log V. log A. log K. 
1:80414 1:66181 185854 0-71600 
1:80140 1:66932 1:86747 0°79239 
179729 1:68395 1:88649 0:91381 
1°78533 1°71517 1:92942 1:11059 
1°78247 1:72428 194151 1:15534 
1:77305 1:74.974 197681 1:32838 
176641 1:76343 1-99782 1:40312 
1:76193 1:78604 0:02531 1°55388 
1°75587 1:80003 0:08279 164147 
Let E be the watts of the lamp and & the efficiency or 
candles per horse-power. Then 
pe K 746, 
— AV 5 
and if we calculate the logarithms of the efficiency corre- 
sponding to each electromotive-force value, and compare these 
with four times the value of the corresponding electromotive 
force, we have the following table :— 
log &. 4 log v. 4 log v—log k. 
206839 664724 4°57885 
2°13834 6°67728 4°53894 
2°21611 6°73580 4-51969 
2'33879 686068 4:52189 Mean 
2°36229 689712 453483 } =4:52968 
2°47457 6'99896 4°52439 | =log 33860 
2°51461 705372 4°53911 
2°61527 714416 4°52889 
2°63137 720012 4:56885 
. Excepting the first and last values, which are the result of 
observations on the candle-power at extreme values, the inter- 
mediate figures are not very far from constant, and indicate, 
as a first rough approximation, that efficiency varies as the 
fourth power of the electromotive force. 
At both high and low candle-powers the comparison of the 
light with a standard candle is difficult. Im one case an 
excess of red, and in the other an excess of violet rays makes 
the comparison of the naked lights much more difficult at 
extremes, and, as is well known, the efficiency for very high 
or low candle-power must be stated for a definite radiation. 
The only other comparison between these two variables 
