588 



Thus it appears that the powder which inflames more rapidly has 

 a much greater initial force, being more concentrated in its action ; a 

 quick burning powder therefore is better for ordnance of small length, 

 such as mortars and iron howitzers. The different results produced by 

 powder of different quality bave, according to the author, been en- 

 tirely overlooked in the hitherto received theory. This theory, which 

 considers the secondary force, namely, the elasticity of the fluid only, 

 and takes no account whatever of the enormous impulsive, or initial 

 force, produced by the sudden conversion of the powder into an elastic 

 fluid, is that which regulates the system upon which ordnance are at 

 present constructed ; hence the reason why large guns are so liable 

 to burst, so much so, that it has been said that no gun larger than a 

 32-pounder is safe to fire. From the variety of experiments made 

 by the author, he arrives at the conclusion, that when powder is of the 

 same quality, and confined in chambers of similar form, but of differ- 

 ent sizes, the initial force varies, within certain limits, in the ratio of 



-j where w is the weight of the powder and w' of the ball. 



Thus were this new theory recognized, the question of the in- 

 crease of strength with increased thickness of metal, would wear an 

 entirely new aspect. So far from the metal in large guns diminishing 

 in strength in the proportion assumed, it will be a matter for inquiry 

 how it resists the great strain to which it is subjected, rather than 

 why it yields ; for we find from the experiments described above, 

 that a 68-pounder gun, which has a calibre of twice the diameter of 

 a 9-pounder gun, must, when fired with the same proportionate 

 charge of powder as the latter, continually be subject to as great a 

 strain as the latter would suffer if always fired with the proof charge, 

 which is three times the quantity of the ordinary service charge. 



The Society adjourned to January 6, 1859. 



