52G REPORT — 1894. 



He believed that with some very hrisante Belgian powder with which 

 he experimented a chamber pressure of 24,022 atmospheres (157"6 tons 

 per square inch) had actually been reached, while with an ordinary powder 

 and a realised energy of nearly the same amount the maximum chamber 

 pressure was only 3,734 atmospheres (24-5 tons per square inch). With 

 the brisante powder this erroneous conclusion was doubtless due to two 

 principal causes, viz. — 



1st. To the seat of the small bullet being at a considerable distance 

 from the charge. Under these circumstances, as later on I shall have 

 occasion to describe experiments to prove, a far higher pressure induces 

 motion in the bullet than is due to the tension of the gases in a state of 

 rest. 



2nd. To the brisante nature of the powder. With such powders, 

 especially in large cliarges, it has been proved that great variations of 

 pressure exist in the powder chamber itself, in some cases the pressure in- 

 dicated at one point of the chamber being more than double that at others. 



It has further been proved that with brisante powders waves of 

 pressure of great violence sweep from one end of the chamber to the other, 

 and if Cavalli's small bullet were acted on by one of these waves an ex- 

 ceedingly high pressure would, without doubt, be indicated. 



3rd. A third cause of error, but much slighter, is due to the muzzle 

 pressure, when the small bullet quits its barrel, being both abnormally high 

 and also abnormally sustained ; hence there will be a considerable incre- 

 ment of velocity after the bullet quits tlie gun. 



It is but fair to add that the results obtained by Cavalli with the 

 powders which he terms ' inoffensive ' are, if some correction be made for 

 the third cause of error alluded to above, not far i-emoved from the truth. 



A Prussian Artillery Committee, under the presidency of General 

 Neumann, made, in 1854, a great improvement on the plan proposed and 

 employed by Cavalli. 



Their mode of procedure consisted in drilling a hole in the powder 

 chamber of the gun to be expei'imented with, in which hole was placed a 

 small barrel of about six inches in length. Now, when the gun was 

 loaded, if in the small barrel were placed a cylinder of a length equal to 

 that of the projectile, it is clear that, on the assumption that the pressure 

 in the powder chamber is uniform, the cylinder and the projectile will 

 describe equal spaces in equal times ; hence, if we determine the velocity 

 of the cylinder when it quits the small barrel, we know the velocity of the 

 projectile when it -has moved six inches from its seat. By altering the 

 length of the column of the cylinder placed in the small barrel, and ascer- 

 taining the resultant velocity, the velocity of the projectile at any desired 

 point of the bore can be determined. 



General Neumann's Committee carried out their experiments only in 

 very small guns and with the grained powder used in those days. Their 

 results were probably not far from the truth, although subject to one of 

 the defects to which I alluded in reviewing General Cavalli's experiments. 

 Indeed, these results were examined and entirely contirmed by the dis- 

 tinguished Russian artillerist General Mayevski, in a very elaborate 

 memoir ; but the experiments of the Prussian Committee were chiefly 

 remarkable for being, so far as I know, the first to recognise the variation.? 

 of pressure which may exist in the powder chamber itself, variations which 

 may, under certain circumstances, attain great magnitude, and to whiclj 

 I have already drawn attention. 



