comparing light sources

1

Andrew Ure.
A Dictionary of Arts, Manufactures and Mines...
London: Longman, Orme, Brown, Green & Longmans, 1839.
Page 248.

A few years ago I made a set of experiments upon the relative intensities of light, and duration of different candles, the results of which are contained in the following table.

Number in a pound. Duration of a candle. Weight in grains. Consumption
per hour
in grains
Proportion of light. Economy of light. Candles equal one Argand.
h. m.
10 mould 5 9 682 132 12¼ 68 5.7
10 dipped 4 36 672 150 13 65½ 5.25
8 mould 6 31 856 132 10½ 59½ 6.6
6 ditto 7 1160 163 14 2/3 66 5.0
4 ditto 9 3.6 1707 186 20¼ 80 3.5
Argand oil flame 512 69.4 100  

A Scotch mutchkin, or ½ of a gallon of good seal oil, weighs 6010 gr., or 13 1/10 oz., avoirdupois, and lasts in a bright Argand lamp 11 hours 44 minutes. The weight of oil it consumes per hour is equal to 4 times the weight of tallow [consumed in a hour] in candles 8 to the pound, and 1/7 [sic, a "3" is missing, should be "3 1/7"] the weight of tallow in candles 6 to the pound. But, its light being equal to that of 5 of the latter candles, it appears from the above table that 2 pounds weight of oil, value 9d. in an Argand, are equivalent in illuminating power to 3 pounds of tallow candles, which cost about two shillings. The larger the flame in the above candles the greater the economy of light.

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