Alcoholic Fluids^ Oils, Sfc^ in Lamps. 55 



match be now applied, the oil in the upper part of the tube eva- 

 porates and produces a flame, fresh portions of oil rise to fill the 

 empty space, and thus combustion is maintained. With such 

 a burner there is no shadow ; the reflected image of the flame 

 being seen directly under the true flame. From a number of 

 such burners, in an appropriate glass-vessel, the illumination is 

 brilliant ; and the floating disks are observed to be in continual 

 motion, as if alternately attracting and repelling each other; which 

 proceeds from the film of oil immediately under the mica be- 

 coming expanded by heat. Though such burners, when pro- 

 perly constructed, will maintain combustion for many hours, 

 if the flame is by any means extinguished, they almost in- 

 stantly sink to the bottom. This results from the structure of 

 the mica, and the expansion of the oil by heat. Mica is com- 

 posed of thin plates, which admit oil into their interstices ; and 

 the oil thus admitted, with that on the under surface of the mica, 

 is expanded by the heat of the flame. When the flame is extin- 

 guished the oil cools, and then the mica, being specifically heavier 

 than the oil, necessarily sinks. 



A burner, similar to the one above described, but more appli- 

 cable to ordinary purposes, seems to merit description, as it may 

 be readily constructed, and will be found admirably adapted for 

 a night lamp. In this form, a small light concave shell, or a 

 light concave glass, resembling in miniature that of a watch, or 

 a small disk of card paper, made concave by pressure, and coat- 

 ed with a solution of gum, is used instead of the mica. A small 

 hole is made in the centre, and a piece of sound cork, about the 

 size of a pea, is cemented on the convex side, and over the per- 

 foration. A small perforation 13 then made through the cork, 

 and a rather wide and thin bugle bead is stuck firmly into it, 

 from the concave side of the shell. The only use of the cork is 

 to fix the burner, so as to admit of its being readily adjusted or 

 replaced. When the shell floats on the oil, the upper extremity 

 of the burner should be nearly on a level with the surface of the 

 fluid ; and if the burner be properly fixed in the cork, the shell, 

 glass, or concave piece of paper, will not sink when the flame is 

 extinguished. The quantity of pale rape seed oil (which, in 

 every respect, is the best) that is consumed by a single burner, 

 amounts to about three-fourths of an ounce in twelve hours, 



