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Experiments of Candle Wicks ; and on the effects of 

 Chlorine upon the combustible properties of the Wax 

 of the Candleberry Myrtle. By Mr. John Reid, 

 Member of the South African Institution. 



[Read at the South African Institution.^ 



The fat of the Sheep or the Cow when exposed to tlie 

 temperature of 120° of Fahrenheit melts, and when exposed to 

 the temperature of 500? suffers decomposition, and is con- 

 verted into gaseous compounds consisting of Carbon, Hydrogen, 

 and Oxygen. At this elevated temperature they burn in 

 contact with atmospheric Air, the combination being attended 

 with the extrication of Caloric and Light. 



When a Candle is lighted a portion of Tallow is melted. 

 is attracted by the "Wick till it is brought within reach of the 

 flame, where it is converted into the compounds above- 

 mentioned, which combining with the Oxygen of the Atmos- 

 phere give out Caloric and Light. This Caloric melts another 

 portion of Tallow, which is attracted, decomposed, and under- 

 goes combustion, and thus is a regular supply kept up. 



Combustion requires an elevated temperature ; if therefore 

 any substanee at a low temperature is brought near the flame, 

 it abstracts a portion of Caloric, and causes a diminution of 

 its size, and if brought still more close, or a substance at a 

 lower temperature is made to approach it equally near, it is 

 entirely extinguished. 



These circumstances serve the important purpose of regu- 

 lating the combustion, for if this communication of Caloric to 

 surrounding objects did not take place, and if the combination 

 was effected at a low temperature, the whole mass would suffer 

 almost instantaneous conflagration. When a Candle is lighted 

 or relighted, the Wick either having no Tallow or only a small 

 quantity, is soon consumed, and the flame is forced to descend 

 till it comes near the mass of unmelted matter; in this case, 

 or when the Wick is snuffed too close, the Caloric being 

 abstracted too rapidly, the flame is diminished in size; and on 

 account of its proximity to the mass, melts a greater quantity 

 of Tallow than is required for the proper supply, which 

 accumulates and makes the Candle gutter, causing waste and 

 inconvenience. On the other hand, when a Candle has burnt 

 for some time, the Wick becomes too long, diminishing by its 

 presence the quantity of light evolved by the combustion. 

 This obscuration may be partly owing to the shadow of this 

 opaque body, but is in part owing also to the influence it 

 exerts upon the chemical process which takes place. As the 

 Wick is not consumed, it requires a constant supply of Caloric 

 to keep it at an elevated temperature, which being abstracted 



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