128 MOHR AND REDWOOD'S PRACTICAL PHARMACY. 
F ig. 21. 
Gas-burner. Gas-Burner. Gas-Furnace. 
cylinder of sheet iron, which is covered with black japan 
varnish to protect it from becoming corroded with rust. It 
is four and a half inches in diameter at top, five and a half 
inches in diameter at the bottom, and ten inches in height. 
The air for supporting the combustion of the lamp, is ad- 
mitted through apertures at the bottom of the cylinder, while 
the hot air and products of combustion, escape through a 
number of small holes near the top. There is a door on 
one side of the furnace, which is used for lighting the lamp 
when any apparatus is fixed over the opening above; there 
