Morey on Heat and Laght. 125 
portion of water intimately blended or mixed with these 
vapors, that can be from an excess of oxygen furnished by 
ereating 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 iar 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, ands if the proportions are right, wi il burn without 
ari oad for aught that appears, may he continued while 
the supply lasts. ‘But if the steam be shut eff, 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, thai 
tar or rosin is evaporated at a much lewer temperature, 
which must be increased as the proportion of water decreases, 
in order to furnish the same quantity of light. 
As f understand it, all the heat that is necessary to fur- 
nish the vapors of these substances, is a sufficiency to vola- 
tilize them: and this temperature must be nearly preserved, 
to prevent their condensing, until they issue through the 
apertures to be inflamed. <A red heat is never necessary. 
The stove, or lampstove mentioned, and which I use, is so 
constructed, that after being once filled, it will supply the 
fire regularly and constanily for any defined length of time, 
without any further attention. For instance—if a cylinder 
of sheet-iron, say two feet long, four inches in diameter at 
top, and about five at the Porn! having a grate one or two 
mches from the bottom, be filled with oe al; an aper- 
ture being made one or two inches above the grate, the 
coal, ignited at the bottom, (the top being covered,) will 
burn only at the bottom, whether the air be led directly 
across the coal and taken from the opposite side, or made 
to pass down through the grate, and led away from the 
bottom. Nor does it make any difference, whether the air 
let in below or at the grate, passes up through the coal, and 
is let out at the top; the quantity being regulated by a 
register, from a well known principle, it can ae only at 
the bottom. As the coal consumes then, it settles down, 
