Management of Light in Illumination. 203 



0.69521 to 1.86660; but the tallow candle furnishes 

 115° of light. 



When a proper allowance is made for the difference 

 between the quantities of light furnished by these two 

 candles, it will appear that the cost of the light fur- 

 nished by the tallow candle is to the cost of that 

 furnished by the wax candle as 0.60454 to 1.86660, or 

 as one to three nearly, when the quantities of light are 

 equal. 



But in the careless manner in which tallow candles 

 are commonly used, the light they furnish is more 

 expensive. 



The candles usually burned in the workshops of 

 tradesmen at Paris, such as joiners, cabinet-makers, 

 etc., are such as are sold in bundles of eight to the 

 pound. These candles cost two sous (= four farthings 

 sterling) each ; and they seldom burn longer than 

 five hours. This gives 0.8 of a farthing for the cost of 

 the light furnished by one of these small candles dur- 

 ing one hour ; but the quantity of light so furnished is 

 far from being equal to that furnished by the standard 

 wax candle. Instead of giving 100° of light, they sel- 

 dom furnish 75° and frequently give less than 50°, that 

 is to say, whenever they burn with a long wick and 

 stand in need of being snuffed, which very often hap- 

 pens. 



From the result of all my observations I have been 

 induced to conclude that the light actually furnished 

 by tallow candles amounts to little more than half what 

 they ought to furnish, if well managed ; and that the 

 light they give costs nearly half as much as the light 

 furnished by wax candles, which, as is well known, sel- 

 dom stand in need of snuffing. 



