VELOCITY AND PRESSURE INSTRUMENTS. 
377 
The object of the experiments from which the above rounds are taken was 
to ascertain the gain in velocity obtained by increasing the length of bore 
of the original 85-ton guns by 36 ins. If it be required to calculate the 
mean pressure at any point, it is necessary to measure the velocity of the 
projectile, during the first part of its motion in the bore, over much shorter 
intervals than a foot. Experiments of this nature were carried out in the 
10-in. and 11-in. guns, the distance between the cutter plugs at the seat of 
the projectile being 0*2 ft. or 2*4 ins., as shown in Plate V., Pig. 3. The 
following table* gives the data obtained with the chronoscope for calculating 
velocity and pressure in the bore of the 10-in. gun. Charge, 70 lbs. pebble 
powder; weight of projectile, 800 lbs.; muzzle velocity, 1527 ft. 
Distance 
from seat 
of shot. 
Time 
observed 
at plugs. 
Total time 
from seat 
of shot. 
Time taken 
by shot to 
traverse 
distance 
between 
plugs. 
Mean 
velocity 
over 
space 
between 
plugs. 
ft. 
sees. 
secs. 
secs. 
ft. 
0-00 . 
•oooooo 
•002683 
22 
0-06.. 
■000000 
•002683 
•001096 
183 
0-26...... 
•001096 
•003779 
- 
•000515 
388 
0-46. 
•001611 
•004294 
•000356 
562 
0-66. 
*001967 
•004650 
•000305 
656 
0*86. 
•002272 
•004955 
•000276 
725 
1-08...... 
•002548 
•005231 
•000488 
820 
1-46. 
•003036 
•005719 
•000433 
924 
1 - 86 ...... 
•003469 
•006152 
•000400 
1000 
2*26....... 
•003869 
•006552 
•000375 
1065 
2 - 66 ...... 
•004244 
•006927 
•000703 
1138 
3-48.. 
•004947 
•007630 
•000658 
1215 
4-26.. 
*005605 
•C08288 
•000629 
1273 
5-06. 
•006234 
•008917 
•001192 
1342 
6-66. 
•007426 
•010109 
•001128 
1418 
8-26. 
•008554 
•011237 
Prom these data are deduced, by correction and interpolation, the times 
occupied by the shot in passing over each two-hundredth (-g-icr) of & foot. 
Prom the differences of these times are calculated the mean velocities over 
* “Researches on Explosives: Fired Gunpowder, 5 ’ by Captain Noble (late R.A.) F.R.S., &c., 
and F. A. Abel, F.R.S., President C.S., &c. From the “ Philosophical Transactions of the Royal 
Society,” Part. I., 1875. 
