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and we helve then only those nflturcil fireworks, which cis much surpass the 
imitated; as heaven is higher than the earth, but which impart a dreadful fear 
to the astonished inhabitants of those countries, where such tremendous scenes 
are carried on, 
Hence in opposition to Dr. Darwin, but with a becoming deference, we 
conclude, that as in our frames a continued combustion is going on pro¬ 
ductive of animal heat * the sine qua non of life, and sensation, so there is a 
so replete with the electric fire, except in the two great eruptions of 1767 and 1779- The electric fire, 
in the year 1779, that played constantly within the enormous black cloud over the crater of Vesuvius, 
and seldom quitted it, was exactly similar to that which is produced, on a very small scale, by the 
conductor of an electrical machine communicating with an insulated plate of glass, thinly spread over 
with metallic filings, &c. when the electric matter continues to play over it in zig-zag lines, without 
quitting it. I was not sensible of any noise attending that operation in 1779* whereas the discharge 
of the electrical matter from the volcanic clouds during this eruption, and particularly the second and 
third days, caused explosions like those of the loudest thunder, and, indeed, the storms raised, evi¬ 
dently by the sole power of the volcano, resembled, in every respect, all other thunder-storms, the 
lightning falling and destroying every thing in its course. 
Out of these gigantic and volcanic clouds, beside the lightning, both during this eruption and that 
of 1779, I have, with many others, seen balls of fire issue, and some of a considerable magnitude, 
which, bursting in the air, produced nearly the same effect as that from the air-balloons in fire-works, 
the electric fire which came out having the appearance of the serpents with which those firework bal¬ 
loons are often filled. The day on which Naples was in the greatest danger from the volcanic clouds, 
two small balls of fire, joined together by a small link like a chain-shot, fell close to my casino at Po- 
silipo; they separated, and one fell in the vineyard above the house, and the other in the sea. 
The Abbe Tata, in his printed account of this eruption, mentions an enormous ball of this kind 
which flew out of the crater of Vesuvius while he was standing on the edge of it, and which burst in 
the air at some distance from the mountain; soon after which he heard a noise like the fall of a number 
of stones, or of a heavy shower of hail.” 
After the eruption had ceased, when Sir William Hamilton ascended the mountain, he thus writes, 
“ While we were on the mountain, two whirlwinds, exactly like those that form waterspouts at sea, 
made their appearance; and one of them, which was very near us, made a strange rushing noise, and 
having taken up a great quantity of the fine ashes, formed them into an elevated spiral column, which, 
with a whirling motion, and great rapidity, w r as carried toward the mountain of Somma, where it 
broke, and was dispersed. As these were evident signs of an abundance of electricity in the air at this 
time, I have no doubt of this having been also an electrical operation.” 
* The ingenious Dr. Crawford appears to have been the first who attempted to ascertain by direct 
expeiiments the cause of animal heat as dependant upon the air. In an elaborate work he maintains, 
that the blood, which is returned to the lungs, is highly charged with phlogiston ,—that the air having 
a greater affinity for phlogiston than the blood, attracts to itself that principle , and having in conse¬ 
quence a less capacity for heat than before, it parts with a portion of its heat,—and as the capacity of 
blood for heat is at the same time increased by the separation of the phlogiston, the heat, detached 
from the air, is fixed in a quiescent or latent state in tne blood:—and that the blood in the course of 
the circulations absorbing phlogiston, and thereby having its capacity for heat diminished, part of it 
(in proportion to the quantity of phlogiston absorbed) breaks out in the form of sensible or moving 
heat, and hence the cause of animal heat. 
It required a very strong philosophic conviction in any one to depart from a proposition at that 
time so generally received. But having made many experiments, when enquiring into this subject. Dr. 
