Morey on Heat and Light. 125 
ortion of water intimately blended or mixed with these 
vapors, that can be from an excess of oxygen furnished b 
creating a very strong current of air, with a high flue. With 
water it is effected much more conveniently, and without 
carrying off any part of the heat from the room. Another 
advantage is, it carries along with it the whole of the tar and 
consumes it. For instance, if into a piece of a gunbarrel 
about six inches long, tar be made to flow regularly at one 
end, a quantity of steam let into the same end, and the iron 
kept at a temperature below or at a red heat, the vapors 
issuing through small holes at the other end, may be infla- 
med, and, if the proportions are right, will burn without 
smoke, and for aught that appears, may be continued while 
the supply lasts. But if the steam be shut off, and the tar 
contains no water, the small apertures and the barrel itself 
will in a short time, become filled with a coaly residium. 
Another advantage in using a proportion of water is, that 
tar or rosin is evaporated at a much lower temperature, 
which must be increased asthe proportion of water decreases, 
inorder to furnish the same quantity of light. 
As I understand it, all the heat that is necessary to fur- 
n only at the bottom, whether the air be led directly 
across the coal and taken from the opposite side, or made 
