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MINUTES OF PEOCEEDINGS OF 
of powder, properly placed in such a machine, may produce as violent an effect as a 
bullet twice its weight moving with a velocity of 1400 or 1500 ft. per second.”* 
In order to discover what effect this action had on the velocity of the 
bullet, Bobins placed 12 pennyweights of powder at the bottom of a musket 
and a bullet 11J ins. from the bottom of the bore, and found that the velocity 
imparted was 1400 ft. per second instead of a calculated velocity of 1200 f.s. 
without the action in question. When the same quantity of power was 
scattered through the whole space, the velocity was only 1100 f.s. 
By placing a bullet 16 ins. in front of the charge in a “ good Tower 
musket,” he found that “ the part of the barrel just behind the bullet was 
swelled out to double its diameter, like a blown bladder, and two large 
pieces 2 ins. long were burst out of it.” 
We have every reason to believe that the action here referred to does 
exist, and also that it is local and does not extend throughout all the space 
in which the pressure of the powder acts. Under these circumstances, the 
thinner the confining surface at the point of action the more injurious would 
be the effects produced. With a thick wall, as in a gun, the action would 
be more distributed, and, though it might indent the surface of the bore as by 
a blow, it might not succeed in endangering the structure of the gun. Bor 
the same reason it is more than likely that any action of the sort would not 
appreciably interfere with Branford's results, as well on account of the great 
mass on which he received the pressure as on account of the fact that a 
small motion of the weight had to take place before any gas could escape. 
It will be observed, however, that though Bumford's experiments are most 
valuable in showing the extraordinary force of fired gunpowder and its 
pressure when occupying various spaces; yet, because they leave out of 
account the rate of combustion, on which mainly depends the amount of 
relief given by the motion of a shot in a gun, they do not help us practi¬ 
cally. We consequently find that succeeding experimenters have turned 
their attention to some method of determining the explosive force of powder 
which includes this most important element. 
Bodman is the next whose experiments we must consider. He endea¬ 
voured to measure the pressure in the bore from the recoil of the gun, 
swung as a pendulum, by causing it to trace a curve on a revolving cylinder. 
As, however, the whole space of recoil was less than an inch, nothing more 
than a general outline of the pressure could be obtained. He says :—f 
“ The curves described show that the gun and shot had acquired one-half of 
their final velocity in about one-fourth of the time required for the shot to pass 
from its seat to the muzzle of the gun; therefore the mean pressure in the bore of 
the gun, during the first fourth of that time, must have deen double that for the 
whole time, or = 18,182 lbs. (8 tons) per square inch. They further show that 
the shot and pendulum had acquired one-fourth of their final velocity in about 
one-sixteenth part of the whole time aforesaid, and that the mean pressure during 
the first sixteenth part of that time was = 86,264 lbs. (16*2 tons). And the 
pressure will be still greater during the lower rates of velocity, amounting to 
probably 50,000lbs. (22*3 tons) per inch; and this estimate is for a statical 
^ “ Ency. Brit.” Gunnery. 
f “ Experiments on Metals for Cannon and Cannon Powder.” Bodman. 
