NATURAL 
Previous to the relation of the 
experiments, it is necessary to ob- 
serve, that the Russian fir-black is 
three or four times more heavy, 
thick, and unctuous, than that kind 
of painter’s black which the Ger- 
mans cail kien-rahm. The former 
is gathered at Ochta, near St. Pe- 
tersburgh, at Mosco, at Archangel, 
and other places, in little wooden 
huts, from resinous fir-wood, and 
the unctuous bark of birch, by 
means of an apparatus uncommonly 
simple, consisting of pots without 
bottoms, set one upon the other ; 
and is sold very cheap. The fa- 
mous fine German kien-rahm is 
called in Russia Holland’s black. Io 
what follows, when I speak of raw 
oil, it is to be understood of linseed= 
oil, or hemp-oil; but most commonly 
the latter, The varnish is made of 
five pounds of hemp-oil boiled with 
two ounces and a half of minium. 
For wrapping up the composition, 
r. Georgi made use of Coarse 
hemp linen, and always single, 
‘ 
never double. The impregnations 
and commixtures were made ina 
large wooden bowl, in which they 
stood open till they were wrapt up 
in linen. 
That I may not be too prolix, I 
will select and communicate only 
such of the experiments as were 
most remarkable, and succeeded 
best. 
Three pounds of Russian fir-black 
were slowly impregnated with five 
pounds of hemp-oil-varnish ; andy 
when the mixture had stood open 
five hours, it was bound up in linen, 
By this process it became clotted ; 
but some of the black remained dry. 
When the bundle bad lain sixteen 
hours in a chest, it was observed to 
emit a very nauseous, and rather 
putrid smell, not quite unlike that 
Vou. XXXVI. 
HISTORY. 
of boiling oil, Some parts of ‘it be- 
came warm, and steamed much; 
this steam was watery, and by no 
means inflammable, Eighteen hours 
after, the mixture waS wrapt up, 
one place became brown, emitted 
smoke, and directly afterwards 
glowing fire appeared. The same 
thing happened in a second and @ 
third place; though other places 
were scarcely warm. The fire crept 
slowly around, and gave a thick, 
grey, stinking smoke. Mr. Georgi 
took the bundle out of the chest, 
and laid it on a stone pavement ; 
when, on being exposed to the free 
air, there arose a slow burning 
flame, a span high, with a strong 
body of smoke. Not long after- 
wards there appeared, here and 
there, several chaps,, or clefts, as 
from a little volcano, the vapour 
issuing from which burst into flame. 
On his breaking the lump, it burst 
into a very Violent flame, full three 
feet high, which soon grew less, 
and then went out. The smoking 
glowing fire lasted for the space of 
six hours 3 and afterwards the res 
mainder-continued to glow without 
smoke for two hours longer. The 
grey earthy ashes; when cold; 
weighed five ounces and a half. 
In another experiment perfectly 
similar to the foregoing, as far as 
relates to the composition and quane 
tities, the enkindling did not ensue 
till forty-one hours after the i impreg= 
nation : the heat kept increasing for 
three hours, and then the accension - 
followed. 
It is worthy of remark, that these 
experiments succeeded better on 
bright days, than on such as were 
rainy : and the accension came on 
more rapidly. 
In another experiment, | three 
pounds of Russian fir-black were 
[* FJ slowly 
[sr 
