*30] 
slowly impregnated with three 
pounds of raw hemp-oil; and the 
accension ensued after nine hours. 
Three quarters of a pound of 
German rakm were slowly impreg- 
nated with a pound and a half of 
hemp-oil varnish. The mixture re« 
mained seventy hours before it be- 
came hot andreeking. It then gra- 
dually became hotter, and emitted 
a strong exhalation; the effluvia 
were moist, and not inflammable. 
The re-action lasted thirty-six hours, 
during which the heat was one while 
stronger, and then weaker, and at 
length quite ceased. 
Stove, or chimney soot, mostly 
formed from birch-wood smoke, was 
mingled with the above-mentioned 
substances and tied up; the com- 
pound remained cold and quiet. 
_ Russian fir-black, mixed with 
equal parts of oil of turpentine, and 
bound up, exhibited not the least 
re-action or warmth. 
Birch-oil, mixed with equal parts 
of Russian fir-black, and bound up, 
began to emit a volatile smell; but 
the warmth soon went off again. 
From the experiments of the Ad- 
miralty, and of Mr. Georgi, we 
learn, not only the decisive certainty 
of the self-accension of soot and oil, 
when the two substances are mixed 
under certain circumstances, but 
also the following particulars. 
Of the various kinds of soot or 
lamp-black, the experiments suc- 
ceeded more frequently and surely 
with the coarser, more unctuous, 
and heavier, like Russian painter’s 
black, than with fine light German 
rahm, or with coarse chimney-soot. 
In regard ta oils, only those expe- 
riments‘succeeded which were made 
with drying oils, either raw or 
boiled. The proportions of the 
soots to the oils were, in the suc- 
ANNUAL REGISTER, 1795. 
cessful experiments very various; 
the mixture kindled with a tenth, 
a fifth, a third, with an equal, and 
likewise with a double proportion 
of oil. In general, however, much 
more depends on the mode of mix- 
ture, and the manipulation; and, 
as Mr. Georgi often observed, on 
the weather: for, in moist wea- 
ther, the bundles, after becoming 
warm, would frequently grow cold 
again. 
Tt is in all respects remarkable, 
that it should never till now have 
been observed, that a mixture which 
has been made millions of times, in 
all proportions and quantities, for 
painting of ships, and the outside 
of wooden houses, and sometimes 
intentionally, sometimes acciden- 
tally, left covered or open, a longer 
or a shorter time, should be capable 
of kindling of itself. It is highly 
probable, that, even on this ocea- 
sion it was entirely owing to the at- 
tention of the empress that it was 
made an object of enquiry, or even 
that it was at all observed. 
Before V finish this paper, I will 
just mention a self-accension, not . 
noticed till of late, and that by Mr. 
Hagemann, an apothecary at Bre- 
men. He prepared a boiled oil of 
hyoscyamus, or henbane, in the 
usual way, with common oil. The 
humidity of the herb was’ nearly 
evaporated, when he was called 
away by other affairs, and was 
obliged to leave the oil on the fire. 
The evaporation of the humidity 
was hereby carnied so far, that the: 
herb could easily be rubbed to pow- 
der. The oil had lost its green 
colour, and had become brownish. 
In this state it was laid on the 
straining-cloth, and placed in the 
garden, behind the house, in the 
open air. 
In 
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