1 66 Management of Light in Illumination. 



together at their lower extremities, by binding them 

 with a strong thread, to receive them. The burner 

 must of course be cyhndrical, and its diameter must 

 be such as just to receive the three cord-wicks without 

 pressing them so as to change their form. This 

 burner must have a rim about one tenth of an inch in 

 width projecting outwards, and obUquely upwards at 

 its upper extremity ; and care should be taken to clean 

 this rim every time the lamp is trimmed. The wick 

 being drawn down into the burner by means of the 

 rack, the rim may be cleaned in a moment, with little 

 trouble ; but this must never be neglected. 



These cord-wicks must be previously prepared, by 

 dipping them into melted tallow or melted wax, heated 

 very hot ; and it will be useful to draw them (in the 

 same manner as wire is drawn) through a round smooth 

 hole, made in a thick plate of iron or of brass, before 

 they become quite cold. This will reduce them to the 

 proper diameter, and will at the same time render them 

 smooth, solid, and stiff, and enable them the better to 

 preserve their cylindrical form when they are bound 

 together in bundles (of three) for use. 



It appears to me to be. very probable that a very 

 strong-twisted, hard hempen cord, of about one twen- 

 tieth of an inch in diameter, prepared in a solution of 

 alum, would answer perhaps quite as well as wood for 

 stiffening these cord-wicks, and preventing the oil from 

 rising too freely in the central parts of the cord. There 

 is great reason to suppose that wicks of this kind would 

 be very useful for tallow candles. 



Fig. 5, Plate VIII., is a horizontal section of the 

 cylindrical burner of a lamp containing three cord- 

 wicks, each two tenths of an inch in diameter. 



