224 Count Rumford’s Experhnenls to determine 
experiment (No. 92.) by which it appeared that, calculating 
even upon Mr. Robins’s own principles, the force of gunpow- 
der, instead of being 1000 times, must at least be 1308 times 
greater than the mean pressure of the atmosphere. However, 
not only that experiment, but many others, mentioned in the 
same paper, had given me abundant reason to conclude that the 
principles assumed by Mr. Robins, in his treatise upon gunnerv, 
were erroneous ; and I saw no possibility of ever being able to 
determine the initial force of gunpowder by the methods he had 
proposed, and which I had till then followed in my experiments. 
Unwilling to abandon a pursuit which had already cost me 
much pains, I came to a resolution to strike out a new road, 
and to endeavour to ascertain the force of gunpowder by actual 
measurement , in a direct and decisive experiment. 
I shall not here give a detail of the numerous difficulties and 
disappointments I met with in the course of these dangerous 
pursuits; it will be sufficient briefly to mention the plan of 
operations I formed, in order to obtain the end I proposed, and 
to give a cursory view of the train of unsuccessful experiments 
by which I was at length led to the discovery of the truly asto- 
nishing force of gunpowder; — a force at least fifty thousand 
times greater than the mean pressure of the atmosphere ! 
My first attempts were to fire gunpowder in a confined space, 
thinking, that when I had accomplished this, I should find 
means, without much difficulty, to measure its elastic force. 
To this end, I caused a short gun-barrel to be made, of the 
best wrought iron, and of uncommon strength ; the diameter 
of its bore was \ of an inch, its length 5 inches, and the thick- 
ness of the metal was equal to the diameter of the bore, so that 
its external diameter was 2^ inches. It was closed at both 
