230 Count Rumford’s Experiments to determine 
chamber, the cavity of the long tube was filled up with cold 
tallow, and the screw that closed up its end (which was \ an 
inch long, and but a little more than — of an inch in dia- 
meter) was pressed down against its leather collar with the 
utmost force. The manner of setting fire to the charge was 
as follows : a block of wrought iron, about i± inch square, 
with a hole in it, capable of receiving nearly the whole of that 
part of the short tube which projects beyond the barrel, being 
heated red hot, the end of the short tube was introduced into 
this hole, where it was suffered to remain till the heat, having 
penetrated the tube, set fire to the powder it contained, and 
the inflammation wa s from thence communicated to the powder 
in the chamber. 
The result of this experiment fully answered my expec- 
tations. The generated elastic fluid was so completely con- 
fined that no part of it could make its escape. The report of 
the explosion was so very feeble, as hardly to be audible : in- 
deed it did not by any means deserve the name of a report, 
and certainly could not have been heard at the distance of 
twenty paces ; it resembled the noise which is occasioned by 
the breaking of a very small glass tube. 
I imagined at first that the powder had not all taken fire, but 
the heat of the barrel soon convinced me that the explosion 
must have taken place, and after waiting near half an hour, 
upon loosening the screw which closed the end of the long 
vent tube, the confined elastic vapours rushed out with con- 
siderable force, and with a noise like that attending the dis- 
charge of an air-gun. The quantity of powder made use of 
in the experiment was indeed very small, not amounting to 
