254 F. A. P. Barnard on the Explosive Force of Gunpowder. 
must be much less than this calculation gives. Since therefore 
the powder is not by any means completely burned—not even 
probably on supposition that Piobert’s conclusions in regard to 
the effect of heat and pressure on rapidity of combustion are 
erroneous—before the elastic force of the developed gases ceases 
to act on the projectile, we have reason to suppose that, if our 
determination of maximum theoretic pressure is correct, the. 
velocities computed by our formula will be much in excess of 
those obtained in actual experiment. 
Again, all the circumstances of the actual experiment of which 
the calculation takes no account are in favor of excess on the 
side of the calculation. The weight of the sabot, the envelopes 
of the cartridge, the large amount of heat absorbed by the metal 
the gun, the resistance of the air, &c.—all these particulars, 
if allowed for, would reduce the computed velocity. It is evi- 
dent that there is error somewhere—cither in the determination 
The mean of the computed pressures, in this table, is some- 
what below the assumed pressure :—that is to say, the difference 
is in the right direction, but it is not a sufficient differe 
