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powerful expansion when fired; for the noise was as of many cannon ; this 
alone proves it to be very sudden. 
“ The materials of these earthquakes may be different, but their effects 
will be the same; just as we find the pnlvit fulminant, as it is called, which 
hath some of its materials differing from that of common powder; as also 
aurum fulminant, which is yet more differing, both as to its materials and 
as to its way of kindling, have yet most of the same effects with gunpow¬ 
der, both as to the flashing and thundering noise, and as to the force or 
violence. So that as these are differing in many particulars, and yet produce 
much the same effects, so it is probable, that what is the cause of earth¬ 
quakes and subterraneous thundering, flashings, and violent expansion, as I 
may so call those phenomena observable in those cruet of nature, may be 
in divers particulars differing from every one of these, both as to the mate¬ 
rials, and as to the form and manner of ascension, and yet as to the effects, 
they may be very analogous and similar. So that though I cannot possi- 
but too much resembles those natural calamities, whose causes we at present are endeavouring to 
investigate, as if the miseries of our condition were not enough, without this addition to them of our 
own contriving! 
Gunpowder contains a large proportion of nitre, less of charcoal, and a very trifling quantity 
of sulphur. An hundred pounds of gunpowder possesses seventy-five pounds of nitre, fifteen of char¬ 
coal, and ten of sulphur. This mixture is triturated for ten or twelve hours in wooden mortars, with 
pestles of the same substance; and a small proportion of water is at the same time added. It is then 
passed through several skin sieves to be granulated. The granulated powder is next rested to separate 
the dust, and being then put into a cask by the motion of its parts, the cask being turned by a wheel, 
it becomes glazed, or polished. Chemists and natural philosophers have entertained various opinions 
concerning the violent explosion produced by gunpowder. Some have supposed it to arise from 
water turned into vapour, others to the sudden augmentation of the air. But Ingenhousz seems to 
have given the best explanation of the phenomenon, which will be found hereafter exactly to corre¬ 
spond with the able conjecture of Hook. 
The Abbe Fortana first discovered that an ounce of nitre gave out by the means of fire about eight 
hundred cubic inches of the purest oxygen air: also that an ounce of charcoal heated in a retort, gave 
out about an hundred and fifty cubic inches of inflammable air mixed with a small proportion of fixed 
air. Dr. Ingenhousz put together these two experiments, and calculated the quantity of gas extricated 
from a cubic inch of gunpowder at the moment of ascension, which must amount to five hundred and 
sixty-nine cubic inches of other elastic fluids. And as these must occupy four times this space at the 
degree of heat they must experience, hence it follows, that the air extricated from a cubic inch of 
gunpowder must occupy at least two thousand two hundred and sixty-six cubic inches. Besides this, 
the inflammable air unites with the oxygen air, and produces fresh heat, and vapour, and hence that 
quick and powerful expansion, pressing most where the resistance is least, and pursuing the ball in 
the cavity along which it runs. May not the inflammable air in part, arise from the water of crys¬ 
tallization in the nitre? as it forms one part, out of an hundred, in the producing of gunpowder. 
As to the sulphur, this appears to have no other use than the speedier and more certain ascension of 
the powder: for the poachers, says Mr. Robins, an ingenious waiter, are in the practice of depriving 
powder of its sulphur by heating it with w r arm ashes in a tin plate; and they imagine that by this 
means the force of the powder is increased, and the arms less injured by use. 
2 K 
