THE ROYAL ARTILLERY INSTITUTION. 
93 
It will be seen that the velocity and pressure are both high, which is no 
doubt due to the fact that the pebbles turned out by this machine were smaller 
than the hand-cut pebbles. The results obtained, however, seem to meet the 
requirements of the case, especially as the out-turn of the machine was only 
about 40 barrels a day. The capabilities of the factory in the other processes 
of manufacture are much greater, and so the chopping process was Continued, 
and the pebbles produced by both processes were mixed together, and the 
total out-turn increased from about 100 barrels to nearly 300 a week. 
Colonel Younghusband tried an experiment to compare directly the work 
produced by hand-cut and machine-cut pebbles, not only with the ordinary 
work of the factory, but also with work which had been milled with an in- 
•creased amount of moisture in the charges, with the following results :— 
Stoving. 
Density. 
Experiment. 
M. V. 
Pressures. 
Date. 
No. 
A. 
B. 
C. 
OK. 2. 6. 71 
1-768 
10. 6. 71 
649 
1440 ' 
194 
19-8 
18-6 
HK. 2. 6. 71 
1-782 
10. 6. 71 
650 
1444 
16-7 
15 6 
16-3 
OM. 7. 6. 71 
1-787 
16. 6. 71 
570 
1445 
19-7 
17-4 
16-6 
HM. 7. 6. 71 
1-782 
16. 6. 71 
579 
1437 
19-6 
18-8 
18-0 
It will be seen that there is not very much choice, but that on the whole 
the charges worked “ heavy,” or with the increased per-centage of moisture, 
produce the best results. The more moisture in the powder the less is the 
danger arising from an explosion in the mills, and the charges were accord¬ 
ingly afterwards worked heavy. 
All stovings are proved in the 8-in. gun, and those which meet the required 
tests are at once “ branded,” and passed into the service. The others are 
mixed in a manner calculated to produce the required results. The velocities 
and pressures obtained at proof are always a matter of considerable uncertainty. 
The various stovings may be Compared to different vintages of wine. There 
is an uncertain control over the stovings, but after proof within certain limits 
any brand required can be produced. 
A regular systematic mixing had to be established, so as to work off and 
send away the manufactured powder as speedily as possible after proof. At 
first the stovings were mixed, in a rough and ready way, by two men, each 
taking a barrel and alternately pouring a small portion of the contents into 
another barrel; but very soon a more methodical and satisfactory plan was 
established. 
It appeared to the author that, in order that any system of mixing should 
be a success, some plan must be adopted of securing, that each stoving itself 
should be perfectly uniform. It appeared vain to attempt to work to densities; 
for, from the samples already given, it will be seen that density, taken alone, 
is no criterion of what may be expected at proof. A mechanical system of 
mixing seemed to promise the best results, and this plan was adopted. In 
order to do this with as little trouble as possible, advantage was taken of 
some of the processes of manufacture. 
A glazing, as a rule, consists of four large barrels or churns, each of which 
contains about four small barrels of powder. As these churns revolve at 37 
revolutions a minute for four hours, it may safely be assumed that the con¬ 
tents of each churn are well and uniformly mixed. It by no means follows, 
