125
mum when lamps having an efficiency of 3.1 watts per candle are used.
Thus the maximum efficiency of these
Lamps $1.00 each-Life 600 hrs. at 3 Watts per Candle.
Current costs 10 cts. per ㏋. per hour.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/60/Incandescent_Electric_Lighting_-_Efficiency_-_Fig_4.png/400px-Incandescent_Electric_Lighting_-_Efficiency_-_Fig_4.png)
Fig. 4.
lamps under the conditions assumed is 3.1 watts per candle.
The lamps considered in the case shown in Fig. 4 cost $1.00; all other conditions