THE ROYAL ARTILLERY INSTITUTION. 
99 
the board has arrived again at the original position, it again suddenly changes 
its direction, and the motion proceeds as before. The method of changing 
the direction of the board is by attaching it to an endless chain which passes 
over two small pulleys. In this manner the direction is reversed every time 
of passing over a pulley thus :—- 
Fig-. 9. Scale 
It will be observed in the last samples of firing given, that the density has 
increased. Of course it was at once apparent, if the fault of low velocity 
was due to the moisture, there was no need to attempt to meet the case by 
working to the low limits of density, and the densitv was therefore increased. 
It was found, too, that even 36 hours'’ drying" at 125° Eah. was not sufficient, 
and on the 1st June the temperature of the stove was increased to 135° Eah., 
for 36 hours, with the following result. The moistures are given at the same 
time to serve as a guide, if possible, to what may be expected at proof:—• 
Stoving. 
Density. 
Moisture. 
No. of 
pebbles 
to lib. 
Experiment. 
M. Y. 
Pressures. 
Date. 
No. 
A. 
B. 
C. 
4. 6.72 
1-781 
_ 
, _ 
12.' 6. 72 
1034 
1450 
16-4 
16-8 
16-0 
1. 7.72 
1-780 
— 
— 
12. 7.72 
1109 
1465 
18-2 
18-9 
17-9 
6.- 8.72 
1-784 
•93 
— 
15. 8. 72 
12C0 
1447 
17-5 
19-2 
16-8 
21. 8. 72 
1-781 
1-03 
— 
13. 9. 72 
2 
1493 
20-8 
19-8 
18-0 
2. 9. 72 
1-779 
•9 
— 
4. 10. 72 
37 
1494 
19-7 
18-7 
17-1 
3. 9. 72 
.— 
— 
— 
4. 10. 72 
39 
1492 
17-1 
15-9 
16-4 
1. 10. 72 
1-777 
1-44 
80 
9. 10. 72 
63 
1491 
18-3 
17*4 
17-1 
4. 11. 72 
1-782 
1-38 
80 
8. 11. 72 
110 
1452 
16-4 
16-4 
16-1 
22. 11. 72 
1-781 
1-57 
70- 
2. 12. 75 
143 
1494 
18-5 
18-8 
18-0 
4. 12. 72 
1-779 
1-34 
72 
13. 12. 72 
170 
1475 
18-6 
16-2 
16-9 
14. 12. 72 
1-772 
1-33 
76 
24.12. 72 
187 
1541 
19-7 
19-1 
19-4 
This brings down the manufacture to the end of 1872, and it will be ad¬ 
mitted there is a considerable improvement on the state of matters which 
obtained a year before. Not only has the velocity been very much increased, 
but the pressures have been very considerably reduced. This latter point is 
mainly due to the increase in the size of the pebbles. Instead of being about 
140 to a pound, they are now between 70 and 80, as shown by the column of 
figures. It will be observed that, with the introduction of a new proof gun, 
there is a considerable rise in the average velocity. This is, no doubt, due 
to the fact that in the old gun the velocity had fallen off by the wear 
of the bore. It is not possible exactly to say how much, but evidently it is 
some 30 or 40 feet in 1200 rounds. Staving 3. 9. 72 is the first sample 
with the machine described, as worked out by the author on Captain Smith's 
principle. It not only gave much better pebbles, but a much larger per¬ 
centage—about 80 per cent. This machine has ever since continued in 
constant operation without mishap, and has done the greatest amount of the 
work of granulation or pebble-cutting. The sifting arrangement in use with 
