THE ROYAL ARTILLERY INSTITUTION. 
97 
proofs were right, and sometimes they were too low—in which case they were 
re-dried, or mixed with others that were too high. 
Sieving, 
Density. 
Experiment. 
M. Y. 
Pressures. 
Date. 
No. 
A. 
B. 
1 0- 
8. 2. 72.. 
1-756 
15. 2. 72 
710 
1427 
18-8 
17-5 
16-5 
21. 2. 72.. 
1-754 
29. 2. 72 
739 
1478 
179 
18-2 
17-3 
4 3. 72. 
1-762 
7. 3. 72 
778 
1389 
16-4 
15-6 
15-8 
Do., re-dried ... 
— 
13. 3. 72 
— 
1466 
181 
18-6 
18-0 
23. 3. 72. 
1-762 
8. 4. 72 
900 
1430 
20-3 
19-1 
17-8 
The last sample, it will be observed, shows a falling off in the powder, and 
the reason is to be explained as follows. A new machine on Colonel 
Younghusband's principle had been made, and had just then come into 
operation. It turned out so large a quantity of pebble as to allow of the 
more expensive process of cutting by knives being dispensed with. The machine 
was calculated to give pebbles as large as with the knives, but evidently there 
was a fault somewhere. On examination it was found that there were a great 
number of flakey pebbles, of the description of cubes, divided down the middle. 
They thus were in length and breadth of the proper dimensions, but in 
thickness only half of what they ought to be. This, in the opinion of the 
author, was due to the faulty principle of the second pair of rollers, which did 
not allow of the strips extending outwards, as they were being cut. Though 
they were very detrimental to the proof of the powder, they could not be 
removed by the ordinary method of sifting. He succeeded in removing them, 
however, by the device of an oblong mesh of the following pattern :—- 
Fig-. 7. Scale 
S' 
lr>' 
1 
J _ y 
H- 
j l 
u u 
When being sifted, the flakey pebbles tilted on their edges and passed 
through, while the ordinary pebbles were retained. It was found that the 
system of re-drying was rather troublesome, as it occupied the stoves 
frequently when new powder was required to be dried; and, as 36 hours' 
drying could be given without extra inconvenience, the time of drying was 
increased on 1st April, 1872, from 24 to 36 hours, at the old temperature of 
125° Fall. The following are some of the proofs :— 
| S toying. 
Density. 
Experiment. 
M. V. 
Pressures. 
Date. 
No. 
A. 
B. 
C. 
12. 4. 72. 
1-756 
| 19. 4. 72 
815 
1428 
17-6 
18-2 
16-3 
22.4. 72. 
1 1-752 
26.4 72 
923 
1455 
21-8 
21-8 
19-6 
10. 5. 72. 
1-772 
i 17.5.72 
937 
1408 
15-2 
15-3 
14-8 
Do., re-dried... 
— 
| 29. 5. 72 
1002 
1507 
21-6 
21-2 
17-7 
13. 5. 72. 
1-777 
j 17. 5. 72 
940 
1452 
15-3 
14-9 
14-1 
