Mr. Thompson^ Experiments 
I had remained in this fttuation fome minutes, and almoft 
defpaired of* the experiment’s fucceeding, when the pox der 
exploded, but with a report infinitely lefs than what I expend, 
the noife not greatly. exceeding the report of a well- charged 
wind gun ; and it was not till I faw the pendulum in motion' 
that I could be periuaded that the bullets had been difeharged, 
I found,, however, upon examination, that nothing was left in 
the barrel, and from the great number of fmall particles of 
revived metal that Were difperfed about, I had reafon to think 
that all the powder had exploded. 
The bullets ft ruck the pendulum nearly in the center of the 
target, and both of them remained in the wood : and I found, 
upon making the calculation, that they had impinged againftit 
with a velocity of 428 feet in a fecond. 
If we now fuppofe that the force of aurum fultninans arifes 
from the action of an elaftic fluid that is generated from it in 
j: 
the moment of its explofion, and that the elafticity of this 
fluid, or rather the force it exerts upon the bullet as it goes or 
to expand, is always as its denfity, or inverfely as the fpace it 
occupies ; then, from the known dimenfions of the barrel, the 
length of the fpace occupied by the charge (which in this ex- 
periment was 0,47 of an inch), and the weight and velocity of 
the bullets, the elaftic force of this fluid at the inftant of its 
generation may be determined : and I find, upon making the 
calculation upon thele principles, that its force turns out 307 
times greater than the mean elaftic force of common air. 
According to Mr. robins’s theory, the elaftic force of the 
fluid generated from gun-powder in its inflammation is 1 ,000 
times greater than the mean preffure of the atmofphere ; 
the force of aurum fulminant , therefore, appears to be to that 
of gun-powder as 30 7 is to i,ooo, or as 4 is to 13 very nearly. 
7 °f 
