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chamber, which was probably the first that was tried by anyone. 
An enlarged chamber with a muzzle-loading gun is rather a 
more difficult matter to arrange, because in many cases the 
cartridge has to be made to set up and expand in order to enter 
the enlarged chamber properly. 
A much more complicated question than that of the size of 
the bore is that of the powder. To understand this, it is neces- 
sary to be clear generally as to what takes place in the process 
of explosion. The word “ generally ” is used advisedly, for 
it would be rash for anyone to profess to know all that takes 
place. Speaking generally, then, the explosive gas commences 
to be generated by the flash of the tube igniting the surface of 
the adjacent grains of powder, and the flaming gas so generated 
rapidly expands in all directions open to it ; and thus, under the 
pressure of close confinement, rushes violently through the 
interstices between the grains of the entire charge, which 
grains, becoming ignited, burn from their exterior surfaces 
towards their centres. Thus the gas developed rapidly acquires 
sufficient power to drive the projectile up the bore, following it 
up with all the force it acquires from the further generation of 
gas as the grains bum through. Thus it will readily be seen 
that a small grain of powder facilitates rapid explosion by 
burning through very quickly, and in a small charge of powder 
gives the greatest effect. As the charge increases, however, 
there soon comes a point when the interstices between the 
grains become insufficient for the passage of the flame, and, in 
fact, the bore becomes choked, so that a larger grain becomes 
necessary, even where speed is the sole condition to be considered. 
On the other hand, too large a grain is blown out partially 
consumed from the muzzle, and so partly wasted. Neverthe- 
less, so great is the evil of violent action, that it is better to err 
on this side than on the other. A committee was specially 
appointed to investigate the action of powder in the bore of a 
gun, who made a series of experiments in 1870, showing by 
means of Capt. Noble’s chronoscope and plug or pressure gauges- 
the velocity of the projectile and the pressure of gas at various 
points in the bore of a gun. By their labours they arrived at a 
form of grain which gave a prolonged and continued pressure on 
the projectile throughout its passage along the bore, without at 
any one instant causing an excessively high maximum pressure, 
such as would strain the gun disproportionately. This kind of 
powder necessitates an increased charge as compared with that 
which burns more rapidly, because the latter acts at greater ad- 
vantage by performing its work when the space behind the- 
projectile is smaller. It is much better and cheaper to use more 
powder than to injure the gun, and so the slow-burning powder 
is preferred. Obviously, however, it is impossible so to regulate 
