THE ROYAL ARTILLERY INSTITUTION. 
103 
None of the whole pellets, whether made bj the trade or at Waltham 
Abbey, have ever succeeded in giving results at proof equal to those obtained 
with pebble, and it seems strange that the simple fact of splitting them in 
two should have such a beneficial effect. The reason is pretty well under¬ 
stood to be that pressed surfaces are not so readily or regularly inflammable as 
broken surfaces. The mere fact, therefore, of splitting the pellets furnishes 
two broken surfaces which they would not otherwise possess. 
The following proofs of Curtis and Harvey's pebble show that though, 
as a rule, their powder is very uniform, they could not at this time always 
supply the same sort.* 
Lot. 
Experiment. 
m. y. 
Date. 
No. 
1492 . 
16. 9. 72 
17 and 18 
1452 and 1467 
1493 .. 
II 
19 ,, 20 
1483 „ 1498 
1494 .. 
// 
21 „ 22 
1502 „ 1499 
1495 . 
9, 10. 72 
55 „ 56 
1492 „ 1495 
1496 . 
17.10. 72 
76 „ 77 
1415 „ 1408 
1497 . 
// 
78- „ 79 
1414 „ 1407 
1498 ......... 
u 
80 „ 81 
1466 n 1454 
Messrs. Pigou and Wilks had considerable success in meeting the require¬ 
ments of proof as regards velocity and pressure. The following samples of 
proof are given :— 
Experiment. 
Pressures. 
Lot. 
Density. 
m. v. 
Date. 
No. 
A. 
B. 
C. 
C1-758 
3. 1. 72 
525 
1458 
18-3 
18-5 
15-7 
876. 
] 1-776 
// 
526 
1445 
17-1 
16-8 
15 "6 
(.1-789 
it 
527 
1453 
18-4 
17-3 
15-6 
C1-759 
5. 3. 72 
769 
1463 
19-4 
19-6 
17-7 
911. 
4 1-782 
n 
770 
1425 
14-4 
14-4 
14-4 
(.1-763 
a 
772 
1431 
17-2 
16-4 
16-2 
934. 
( 1-788 
i 1-774 
12. 6. 72 
n 
1044 
1045 
1435 
1446 
16-8 
18-4 
17-0 
18-1 
15-6 
16*7 
Prom what has been said, it will be seen that the manufacture and proof 
of pebble-powder had Very greatly improved during 1872. Density, velocity, 
* The following proofs of Curtis and Harvey’s more recent manufacture show a very remarkable 
uniformity 
Lot. 
Date of 
Corrected 
Corrected pressures. 
experiment. 
M. V. 
A. 
B. 
C. 
A. 
17. 8.74. 
1476 
17-6 
17-2 
16-7 
B. 
11 
1474 
17-5 
18-1 
16-2 
C. 
1471 
16-6 
16-6 
16-8 
D. 
n 
1450 
16-4 
16-2 
15-7 
E. 
„ 
1464 
17-6 
16-8 
15-8 
F. 
1471 
17-8 
17-1 
15-3 
G. 
it 
1478 
18-0 
17-7 
15-9 
H. 
5.10. 74 
1475 
16-7 
15-7 
15-8 
I. 
n 
1467 
17-3 
16-3 
16-7 
K. 
ii 
1470 
15-7 
16-3 
16-0 
L. 
ii 
1467 
163 
16-8 . 
15-6 
M. 
1463 
16-3 
16-5 
16-0 
14 
