2 64 Count Rumford’s Experiments to determine 
elastic fluid acted on the weight employed to confine it; con- 
sequently the weight expressed in pounds avoirdupois , which 
measured the force of the generated elastic fluid in any given 
experiment, being divided by 0.73631, will show how many 
times the pressure exerted by the fluid was greater than 
the mean pressure of the atmosphere. Thus in the experi- 
ment, No. 6, where the weight which measured the elastic 
force of the generated fluid was = 504.8 lbs. avoirdupois, it 
is jgi = 685.6 atmospheres. And so of the rest. 
I have said that the diameter of the bore of the barrel, made 
use of in the following experiments, was just £ of an inch at 
its muzzle , and this is strictly true, as I found upon measuring 
it with the greatest care ; but its diameter is not perfectly the 
same throughout its whole length, being rather narrower to- 
wards its lower end : yet the capacity of the barrel being known, 
and also the diameter of the bore of its muzzle , any small in- 
equalities of the bore in any other part can in no wise affect 
the results of the experiments, as will be evident to those who 
will take the trouble to consider the matter for a moment with 
attention. I should not indeed have thought it necessary to 
mention this circumstance, had I not been afraid that some 
one who should calculate the joint capacities of the bore and of 
the vent tube from their lengths and diameters, finding their 
calculation not to agree with my determination of those capa- 
cities, as ascertained by filling them with mercury,, might sus- 
pect me of having committed an error. The mean diameter of 
the bore of the barrel, as determined from its length and its 
capacity, turns out to be just 0.2281 of an inch; the diameter 
of the vent tube being taken equal to 0.07 of an inch, and its. 
length 1.715 inch. 
