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the case shown in Fig. 11, but the lamps are only half as good. The minimum total cost is increased from $294 to $327, and the maximum efficiency is reduced from 2.38 to 2.62 watts per candle.
Lamps 25 cts. each—Life 2400 hrs. at 3 Watts per Candle.
Current costs 10 cts. per ㏋. per hour.
Fig. 12.
The first and plainest inference drawn from these curves is that the maximum efficiency o£ any given lamp is not a fixed one, but varies with conditions outside
