VELOCITY AND PRESSURE INSTRUMENTS. 
371 
the following table is extracted from the Eeport of the Committee on Explo¬ 
sives on the 38-ton 12*5-in. gun. This gun is bored for crusher-gauges in 
seventeen places:—A is in the axis of the bore at the breech end; 1 is 
1 ft. from the end of the bore; 2 is 2 ft. from the end of the bore; and so 
on, up to 16, which is 16 ft. from the end of the bore and 6*5 ins. from the 
muzzle. The regularity with which the pressure decreases as the powder- 
gas expands—the necessary consequence of the law of expansion of gases— 
though partially counteracted by the evolution of gas from the unconsumed 
portion of the charge, which continues to burn until the shot leaves the 
muzzle, is beautifully exhibited by these experiments. 
Table showing the Pressures recorded by the Crusher - Gauges in the Pore of the 
12'5-m. (38-ton) Gun. 
>■6 
§ 
Charge 
Pressure in tons per square inch at 
o 
f-J 
o 
d 
& 
and 
projectile. 
A 
1 
2 
3 
4 
5 
6 
7 
8 
9 
H 
11 
12 
H 
14 
15 
16 
On base 
of shot. 
72 
130 lbs. of'I 
1‘5-in. | 
powder, }■ 
21-5 
22-6 
22-8 
19-2 
13‘2 
9-5 
6-3 
4-0 
2-8 
2-9 
2*4 
2-1 
1-4 
iJ 
1-1 
1-0 
138 
800-lb. | 
cylinder j 
130 lbs. ofl 
1‘7-in. | 
800-lb. ! 
27-3 
26-5 
24‘5 
19*3 
13‘9 
8-9 
4‘8 
3-8 
3-2 
3-1 
2-4 
1-6 
1-4 
1-3 
1-2 
0-7 
139 
cylinder, j 
with gas- j 
check ... J 
130 lbs. of'I 
1‘5-in. | 
800-lb. 1 
cylinder, 
ae-i 
27-7 
19-7 
22-4 
11-9 
9‘4 
5-1 
4-0 
3-1 
3-0 
2-3 
1-7 
1-6 
1*3 
1‘3 
1-0 
21‘2 
140 
with gas- 
ebeck ... 
130 lbs. of) 
2-in. 
800-lb. 
- 28-7 
24-5 
22-8 
18-3 
12*4 
9-5 
4-6 
3‘2 
3-1 
2-6 
2*3 
1-7 
1-6 
1-3 
1‘1 
0-8 
19‘3 
cylinder, 
with gas- 
check ...^ 
III.—THE NOBLE CHRONOSCOPE. 
This instrument is employed, as before stated, for measuring the time 
taken by the shot in passing over certain small successive spaces in the bore 
of the gun, and calculating therefrom the velocity of the shot in passing 
over each space, and ultimately the mean pressure acting on it through this 
space. It is the invention of Captain A. Noble, late R.A.—a member of 
the firm of Sir W. G. Armstrong & Co., in whose works at Elswick the 
instrument was made. 
The following description is taken from the first Progress Report of the 
Committee on Explosives, dated Eebruary 1870, some slight corrections 
