F. A. P. Barnard on the Explosive Force of Gunpowder. 253 
Kind | vq,| Approx |No. of vols. Velocity | V*l<ItY | Votocity | Dif obs, | Dif. cor. | Thich would | 
ous. al. of n.\expansion. observed. | 7; dage computed. Velocity. Velocity, ee eor, 
ae ar 34 1439 | 1596 | 1368 | — 71 | -228 682 
Bel 2 ¢ 28+ | 1563 | 1720 | 1465 | ~ 98 | -255 6899 
oF} 3) } 2i- | 1741 | 1898 | 1698 | -118 275 6842 
«ie ele 43+ | 1370 | 1508 | 1957 | -113 | -2651 1208 
Seyi 5 t 34+ | 1486 | 1624 | 1878 | -113 | -251 7008 
wee] 6) ut 29- 1635 | 1778 | 14' -164 | -80 1274 
ee ie 21 1834 | 1972 | 1630 | -204 342 7329 
#\..8\. 4 61 1378 | 1516 | 1280 | - 9 236 71023 
mel OS 40+ 167 1 16 169 | -307 7259 
aS 10° + 30 1906 | 2044 | 1674 232 370 7461 
erp: s 68 1444 | 1582 | 1287 5 ~295 1567 
| 3/19 45 1742 | 1880 | 1515 | -227 | -8 WB 
1 S| 13) + 34- | 1951 | 2089 | 1688 | -268 | -401 1678 
— }14 xy 2 2098 | 2236 | 1825 | -273 411 7518 
wis} + 22 2239 | 2877 | 1987 | -802 | -440 1539 
1,3 [16 + 19- 2300 | 2488 | 2030 | -270 | -408 7222 
ee 16+ 2324 | 2462 | 2107 217 355 6833 
ST: ae 68- 1240 | 13894 | 1127 | -113 | -267 7665 
ot 4 0+ 1440 | 1594 | 1270 | -170 | -324 7892 
w=} 20) ¢ 38+ | 1723 | 1877 | 2489 | -234 | -38 7959 
een od 1870 | 2094 | 1658 217 | -3871 "511 
{a#/ 22] 4 60+ | 1271 | 1491 | 1124 | -147 | -297 7994 
Bei os 4 1430 | 1580 | 1266 | -164 | -814 7799 
aej24] ¢ 30- 1640 | 1790 | 1482 | -158 | -808 7302 
1 2125] + 22 1780 | 1980 | 1642 | -138 | -288.| 6913 
Mean of pressures, 7369 
leaves the muzzle. A medium sized cannon powder has grains 
three-tenths of an inch in diameter—the largest sized, from six 
to nine-tenths. Piobert gives, as the conclusion arrived at after 
a very long and elaborate series of experiments on the rapidity 
of combustion of powder in lumps, that the combustion advan- 
ees at the rate of half an inch per second. His conclusion is, 
moreover, positive, that neither heat nor pressure affect to any 
sensible degree this rate. A grain of powder 0°=3 in diameter 
would therefore be nearly a third of a second in burning, while 
man’s experiments prove that the shot of a 42 pdr. with 10 
ibs. powder is but little more than five thousandths of a second 
in the gun after the fire takes the cartridge. We may, also, by a 
very simple process of calculation, show that Rodman’s experi- 
mental determination cannot fro 
. gun 
16 calibres length, when the charge is + of the weight of the shot, 
is 1635 pore i t., Which is therefore 
about the space through which the pressure acts on the projec- 
tile. If this pressure were constant, it would expel the ball in 
the time whieh, it would take the ball to move twelve feet after 
; ee po1a9 
leaving the gun—that is to say, in goaet ube of a second nearly, 
