20

A TREATISE ON GAS-LIGHT.

the diameter of the flame, so as to preventthe access of air to its internal part. When itslength is too great for the vertical position, itbends on one side; and its extremity, comingin contact with air, is burned to ashes; ex-cepting such a portion as is defended by thecontinual afflux of melted wax, which is vola-tilized, and completely burned, by the sur-rounding flame. Hence it appears, that thedifficult fusibility of wax renders it practicableto burn a large quantity of fluid by means ofa small wick, and that this small wick, byturning on one side in consequence of its flex-ibility, performs the operation of snuffingitself, in a much more accurate manner thancan ever be performed mechanically. Fromthe above statement it appears", that the im-portant object to society of rendering tallowcandles equal to those of wax, does not at alldepend on the combustibility of the respectivematerials, but upon a mechanical advantagein the cup, which is afforded by the inferiordegree of fusibility in the w r ax: and that, inorder to obtain this valuable object, one of thefollowing effects must be produced : either thetallow must be burned in a lamp, to avoid the