upon Gun-powder, &c. 321 
mean prefiure of the atmofphere, as will be evident to thofe 
who will take the trouble to make the computation. 
Of an attempt to determine the expkfve force of aurum fulmi- 
nans, or a comparifon between its force and that of gun -powder. 
Having provided myfelf with a fmall quantity of this won- 
derful powder* upon the goodnefs of which I could depend, I 
endeavoured to afcertain its explofive force by making ufe of it 
inftead of gun-powder for difcharginga bullet, and meafuring, 
by means of the pendulum, the velocity which the bullet ac- 
quired; and concluding, from the tremendous report with which 
this fubftance explodes, that its elaftic force was vaftly greater 
than that of gun-powder* I took care to have a barrel provided 
of uncommon flrength, on purpofe for the experiment. Its 
length in the bore is 13,25 inches, the diameter of the bore is 
0,55 of an inch, and its weight 7 lbs. 2 oz. It is of the belt 
iron, and was made by wogjion ; and the accuracy with which 
it is finiflied does credit to the workman. 
This barrel being charged with one fixteenth of an ounce 
( = 27,34 grains) of aurum fulminans and two leaden bullets, 
which, together with the leather that was put about them to. 
make them fit the bore without windage, weighed 427 grains 
it was laid upon a chaffing-dilh of live coals, at the diffance of 
about 1 p feet from the pendulum, and again!! the center of the. 
target of the pendulum the piece was directed. 
Having fecured the barrel in fuch a manner that its direction, 
Ihould not alter, I retired to a little diftance, in order to be out 
of danger in cafe of an accident, where I waited in anxious 
expe&ation the event of the explofion,. 
I had 
