Management of Light in Illumination. 161 



of the cotton will be quite covered with small bubbles 

 of air in a few minutes ; or if the wick of a lamp full of 

 oil, or of a candle full of tallow or of wax, be thrown 

 into melted tallow, so heated as to be almost ready to 

 boil, as this heat is considerably greater than that at 

 which water boils, not only the air, but the moisture 

 also, which remains attached to the cotton, will be sud- 

 denly driven out of it. This will occasion a violent 

 effervescence, accompanied by a loud hissing, which, 

 however, will cease entirely in a few moments ; and the 

 cotton will sink down to the bottom of the hot melted 

 tallow, where it will remain perfectly quiet, and free 

 from air bubbles. 



These appearances afford a decisive proof that air or 

 moisture, or both, remain attached to the wicks of lamps 

 and candles; and it is most certain that they must 

 necessarily be injurious to the wick, by preventing the 

 oil, melted tallow, or melted wax from flowing freely 

 over the minute fibres of the cotton. But this experi- 

 ment shows us at the same time how this evil may 

 be effectually prevented. 



By heating melted tallow till it is nearly boiling hot, 

 on throwing into this hot liquid a parcel of clean dry 

 wicks, the air and the moisture will be expelled in a few 

 moments with a hissing noise, and being replaced by 

 the tallow they will be permanently excluded. As soon 

 as the hissing has ceased, the wicks may be taken out 

 of the melted tallow to drip and cool, and when cold 

 they may be cut into proper lengths ; and being wrapped 

 up in clean paper, to preserve them from the dust, they 

 may be preserved for years without change. 



The wicks of tallow candles and of wax candles 

 might be prepared by dipping them for the first time 



VOL. IV, 



