252 F. A. P. Barnard on the Explosive Force of Gunpowder. 
would be necessary, in similar cases, to produce the velocities 
actually observed. The examples which follow, twenty-five in 
number, are taken from the U.S. Ordnance Manual, and exhibit 
the results actually obtained in experimental firing at the Wash- 
ington Navy Yard. As the guns used were all smooth-bo 
and the projectiles round shot, the observed velocity is correct 
for the loss by windage. The formula for this correction which 
experiment has suggested, is, 
— 
c—b 
eas ’ 
in which C is the correction, ¢ and } have the values assigned 
them in the foregoing formule, and A is a constant determined 
by observation, and is usually put =6400 ft. 
The particulars which enter into the calculation for each form 
of gun are the following :— 
: Calibre) Windage |L’gth of bore| Weight of projectile| cp aces, in pounds | 
Kind of gun. in inches. | in inches.| in calibres “in pounds. peter oh pees 
6 pdr. field, 3-67 | 0-09 15°67 6 1-25, 1°50, 2°00 
12 pdr. field, 462 | 010 16-00 123 2, 2°5, 
12 pdr. siege, 4°62 0-10 22 38 8 2, 3, 4. 
12 pdr. 25 cal, | 462 | 0-10 25°00 123 2, 3, 4, 5, 6, 7, 8. 
24 pdr. siege, 582 | 014 18:56 24-25 3, 4, 6, 8. 
32 pdr. sea-coast,| 640 | o15 | 16-78 323 4, 5°83, 8, 1067. 
5°33, 8, 1001 | 
In the table which succeeds, are given the values of v which 
result from the formula when a is made equal to L—I+a; t 
is, when it has the value which belongs to it at the moment the 
shot leaves the muzzle. The columns “approximate values of n 
and “ No. of volumes expansion,” are introduced for convenient 
comparison. The second consists of the values of : at the mo- 
ment of the expulsion of the shot. These numbers are approxl- 
mate, like the values of n. In the calculation, the exact values 
are in all cases employed. The column of pressures contal 
the computed initial pressures which would be necessary to pro 
duce the velocities corrected for windage. 
The results egies: in the following table are certainly sur 
prising. While anything like a close agreement between com- 
tation and observation was hardly to be expected, every reason 
r anticipating a diserepancy would indicate that the computed : 
velocities should be ine not in deficiency; and the — 
mputed pressures in deficiency and not in excess. The for- 
mula assumes that the gases are fully developed before the shot 
begins to move. In point of fact we know that the combustion 
of cannon powder is far from complete eve n the shot 
