INFLUENCE OF ROSIN ON FATTY SUBSTANCES. 327 
cup a cake of any common shaving soap, so as to reduce it 
to a soft consistence, and then mixing intimately with it half 
its weight of our resinous preparation, adding a few drops 
of some odoriferous substance. The same compound forms 
an excellent water proof paste for leather. Boots, when 
treated with it, will soon afterwards take the usual polish 
when blacked, and the soles may be saturated with it, with- 
out danger of soiling the floor, as it does not rub off, while 
the leather is rendered, in a high degree, impervious to water. 
The perfect solution into which rosin passes when heated 
with oil, suggested the possibility of improving in this way, 
the quality of oils used for illumination, and by its reducing 
the melting point of lard, to render that more suitable for 
burning in solar lamps. I therefore, added powdered rosin 
to lard oil, in the proportion of eight ounces of rosin to one 
gallon of oil, and applied a moderate heat, sufficient to pro- 
duce perfect solution. I then filled two solar lamps, equal 
in all respects — the one with lard oil, the other with the 
same, holding the rosin in solution, and regulating the flames 
so as to be as nearly of the same size as possible. I mea- 
sured by the method of shadows, the comparative intensities 
of light, which I found to be as 7 to 5 in favor of the pre- 
pared oil. This burned with a flame of peculiar richness, 
plainly exceeding in density that from the simple oil ; but 
after two hours the flame of the prepared oil began to de- 
cline slowly, and soon became inferior to the other, an effect 
which doubtless arose from the clogging of the wick. I had 
hoped, on account of the perfect solution which the rosin 
seemed to undergo, that the compound would burn freely 
without encountering this impediment ; but in this respect I 
was disappointed, and can only say that if some means can 
be devised for avoiding the tendency to clog the wick, the 
addition of a small portion of rosin to lamp oil or lard, will 
add essentially to its value for burning in solar lamps, by 
rendering it less liable to congeal, and by increasing its illu- 
minating power. 
