340 
MINUTES OF PROCEEDINGS OF 
of howitzers. There is proof that cast-iron guns occasionally possess 
ample strength. This is evidenced by the Lowmoor gun, oval-bored for 
Mr Lancaster, having resisted 2000 service rounds, and by Mr Britten's 
having stood 1486 (1st April, 1863); but the ordinary inequality of endu¬ 
rance, which causes some cast-iron smooth-bored guns to be condemned 
much earlier than others, must attach to the material in any form, and in 
rifled guns would produce a greater number of failures, and failures at an 
earlier stage, in proportion to the greater strain upon them. 
The Committee have had no opportunity of trying guns made of charcoal- 
iron. They have very little confidence in proposals to strengthen cast-iron 
by external envelopes of steel or wrouglit-iron. The process of gradual 
destruction commences with small fissures round the vent; and when 
these have proceeded to a certain extent, the entry of the gas at an 
enormous pressure tends to rend the metal as if by a wedge. No 
external envelop will prevent this action : its only advantage here seems to 
be to make the effect less destructive. The external envelop adds to the 
strength of the cast-iron gun to resist a strain, when there are no fissures 
and no rending action; but this is not the ordinary cause of guns bursting. 
Guns condemned as unserviceable are almost invariably condemned for the 
state of the metal round the vent, and explosions must be generally attributed 
to that cause. Mr Britten has shown that when his gun of 5‘29-in. bore, in 
a 32-pr. block, was burst, it was under a strain exceeding that in the 32-pr. 
rifled gun, in the ratio of 940 tons to 416 tons (Min. 5547); and by the 
same method of comparison it may be show r n that the relative strain under 
the different systems, measured by the average pressure as far as the trunnions, 
multiplied into the resistance, or weight moved per square inch of section, 
was as follows : — 
Table XII. 
Name. 
Relative 
strain. 
Rounds 
fired. 
Remarks. 
Britten . 
620 
1486 
Not hurst. 
Jeffery . 
708 
363 
Burst. 
Scott . 
720 
309 
Burst. 
Lancaster. 
787 
2000 
Not burst. 
Shunt. 
798 
327 
Burst. 
French .. 
923 
104 
Not burst. 
Haddan. 
1171 
215 
Burst. 
There appears to be no good reason why the projectiles should be heavier, or 
fired with a heavier charge, under one system than under another : the material 
fact is, that Mr Jeffery's gun, Commander Scott's, Mr Haddan's, the French, 
and the shunt gun, burst at a stage out of all proportion earlier than the 
apparent excess of strain on them would warrant. It will be observed, how¬ 
ever, that Mr Britten's results are obtained at a cost of much less strain on 
the gun than those of either of the other plans, and the Committee believe 
that if circumstances of urgency warrant the rifling of cast-iron, it may be 
done on this system with less risk than on any other they are at present 
acquainted with. They trust that no such urgency will arise, and that so 
precarious a material will not come into use for rifled artillery. 
