462 
MINUTES OF PROCEEDINGS OF 
Vibrations . 
Our next topic is one of considerable importance, though perhaps not 
generally considered. Whenever a gun is fired the metal will be set into a 
strong vibration, the magnitude of which will depend altogether on the want 
of elasticity in the gun and carriage, and the mode of fixing the gun in the 
trunnion holes. When the gun or rifle is fixed immovably, these vibrations 
will be strong enough to affect the aim, even though imperceptible to the 
eye. Colonel Jacobs, who mentions some experiments he made on this point, 
says that when he fired the rifle he was trying in a mechanical rest, he was 
surprised at the bad results of his practice, but he discovered by grasping 
the barrel when it was fired, that there was a jar, accompanied by a ringing 
sound, at the moment of firing, and that this no doubt was the cause of his 
bad practice. This is also the reason why government rifles are proved from 
the shoulder and not from a rest. The shorter and heavier a piece is the less 
likely it will be to vibrate, so the weight of ordnance should not be reduced 
beyond a certain limit irrespective of strength. Erom the same cause the 
elasticity or hardness of the materials composing gun carriages will also 
be an important item in their efficiency. We cannot however distinguish in 
the present state of knowledge between these vibrations and heat vibrations, 
of which there will be plenty in connexion with the discharge. These are 
only mechanical undulations of an elastic material, while of the latter we 
know nothing; they are more silent, and probably more destructive to the 
weapon than injurious to the aim. It is curious that a gun is primarily less 
heated with ball than with blank cartridge, however the strains on the gun 
which also produces heat are greater in the former case than the latter, both 
from the re-action experienced and the friction. 
We now come to the much controverted recoil. If it is proved that 
during the time the shot is passing along the bore, the axis of the latter has 
altered in direction to any appreciable extent, it is manifest that the error 
ought not to be neglected. Now, taking a particular example, if the trail be 
forced into the ground "*2, which might be the case before the shot has left 
the bore, there would be an increase according to rule of 30 yds. in range, 
for the Armstrong field piece, in distances up to 500 yds. Consequently, the 
effect of an accurate aim would be nullified if the gun were fired in even 
ordinarily soft ground. Perhaps this change of direction might affect the 
initial velocity of the shot, and the two may counterbalance one another, 
while the range remains nearly unaltered ; but if the trail rose through the 
same distance the difference of range would be greater still on this hypothesis. 
I imagine, by electricity, it would be possible to find the time during which a 
shot will be exposed to such influences as I have mentioned; thus the gun 
may be fired by electricity at a given instant, and the shot may break the 
connexion at leaving the muzzle. This time of passage along the bore 
would be useful in a variety of calculations connected with gunnery; and I 
have no doubt by careful experiments, that a result may be obtained, by 
which the action of the powder &c. may be set on a new footing. 
