116 
MINUTES OF PROCEEDINGS OF 
necessity of all for heavy and powerful guns, rifled some hooped cast-iron 
guns on Parrott's plan, but they place greater reliance in smooth-bore guns 
made from their excellent cast-iron on Rodman's plan. 
With regard to the hooped cast-iron guns it is well known that the vent 
is the vulnerable part of a cast-iron gun, and even if the piece were 
strengthened sufficiently to bear the increased strain, the part adjoining the 
vent would rapidly wear away, and cause the destruction of the gun. As 
for steel, its treacherous and apoplectic nature renders it a dangerous 
material for large guns, and gunners would do well not to trust it until 
greater improvements take place in its manufacture. 
The large American smooth-bore guns shaped somewhat like a soda water 
bottle, as suggested by Captain Dahlgren, United States Navy, and cast 
hollow, and cooled from the interior as proposed by Captain Rodman are, 
for cast-iron guns, the best that can be manufactured, and are no doubt 
very formidable pieces, but weight for weight they are inferior to our muzzle¬ 
loading rifled wrought-iron guns. 
Por, supposing the American cast-iron guns are as durable and as little- 
liable to burst as our sinewy guns of wrought-iron, and that their apocryphal 
charges are actually used, our guns possess the great advantage of being 
able to pierce armour plates with shot, nay even with shell , which the 
American guns could only crush or f * * rack" with solid shot; but perhaps this 
statement wants some demonstration. 
Mode of estimating gun power. 
Now the correct mode of estimating gun power is to calculate the 
( W'lft \ 
-fyf} or the dynamical force of the shot at various ranges, but 
to find out the comparative penetrative effect against armour plates it is 
necessary to divide the vis viva by the diameter of the shot, for it is one 
of the laws established by experiment* that when the projectiles are of a 
hard material, such as steel or chilled iron, the perforation is directly pro* 
portional to the “ work," (vis viva) in the shot,t and inversely proportional 
to its diameter. 
In order therefore to compare our modern heavy guns with their rivals as 
well as with their predecessors, the actual vires vivee (in foot tons) of repre¬ 
sentative guns are given in the following table. 
The manufacture of this gun continued during night and day for sixteen months, and the cost of 
the piece is £15,750. The breech-loading arrangement is complicated, and some time would be 
necessary to go through the different operations in loading. (Report on the artillery at the Paris 
Exhibition by Lieut.-Colonel C. H. Owen, R.A., in the “ Illustrated London News,” August 31, 
1867). 
* See Captain W. H. Noble’s valuable Report on the penetration of armour plates, a blue book 
published 1856 by the War Office. 
f “ Energy ” has lately been used as an equivalent for vis viva, but it is scarcely expressive 
enough unless we call to mind its Greek derivation; 
