376 
VELOCITY AND PRESSURE INSTRUMENTS. 
The loading of the gun is conducted as follows :— 
The cartridge is made up to the required diameter; it is then inserted 
into the shot-chamber, the projectile is next pushed home gently until a 
stop on the rammer comes into contact with the face of the muzzle. Thus 
the head of the shot is brought to the same position in each round, and the 
cartridge always touches the base of the projectile. 
The crushers and cutting plugs are then inserted into their respective 
holes and screwed home. 
Finally, the wires of the cutting plugs are connected with the main wires 
leading to the instrument, and the tube is inserted in the vent. 
After the discharge, the first operation is to wash out the gun; all the 
plugs are then removed and the holes dried preparatory to another round. 
The coppers are taken from the crushers, stamped with the number of the 
round, and the measurements recorded. 
The following table, extracted from the Report of the Committee on the 
IS’h-in. 38-ton gun, shows the velocity of the shot in passing over each 
foot of the bore from its initial position, and the pressures recorded by the 
crusher-gauge. Charge, 130 lbs. 1‘5-in. cubical powder; projectile, 800 lbs. 
No. or 
letter 
of 
plug. 
Mean of 4 rounds. 
Mean of 3 rounds 
with gas-checks. 
Pressure. 
Velocity. 
Difference 
in 
velocity. 
Pressure. 
Velocity. 
Difference 
in 
velocity. 
tons per 
tons per 
sq. in. 
ft. 
ft. 
sq. in. 
ft. 
ft. 
A 
23-8 
23*1 
1 
23-8 
23-6 
2 
22-5 
22-2 
137 
125 
3 
19-9 
533 
28-0 
540 
670 
665 
4 
14-2 
214 
16-0 
230 
914 
895 
5 
11-0 
127 
11-4 
130 
1041 
1025 
6 
7-0 
69 
6-9 
72 
1110 
1097 
7 
3-8 
55 
3*9 
57 
1165 
1154 
8 
2-9 
47 
2-9 
49 
1212 
1203 
9 
40 
42 
1252 
1245 
10 
34 
36 
1286 
1281 
11 
29 
31 
1315 
1312 
12 
1-4 
25 
1*5 
27 
1340 
1339 
13 
1-6 
21 
1-7 
23 
1361 
1362 
14 
If 
18 
1*5 
20 
1379 
1382 
15 
1-1 
16 
1-3 
18 
1395 
_ 
1400 
18 
0-6 
14 
0-5 
16 
1 
1409 
1416 
