32 
MINUTES OF PROCEEDINGS OF 
the rolls,, or rather the chance selection of the pair used, determined the 
size of the first bars which obtained the name of Thorneycroft's bars, 
simply because they were made at the Shrubbery Iron Works, which were 
formerly more generally known by the name of Tliorneycroft's. A target 
formed of these bars secured together, (in addition to the tongue and 
groove,) by a bolt passing through them, was found to offer such resistance 
to shot as to warrant the belief that if reduced to 10 x 4§-in., the 
defence would still be found sufficient. An embrasure was therefore con¬ 
structed of bars 10 x 4f-inch having several feet of masonry above them; 
on this occasion, the bolt used in the former experiment to secure the 
bars together was dispensed with, as it was considered that sufficient 
solidity would be obtained by the weight of the masonry above. This 
embrasure stood the most severe tests without shewing any signs of weak¬ 
ness ; salvoes from 68, 80, 40, and 32-pr. guns were fired against it, 
apparently without damaging the structure, and it was with reason thought 
that an embrasure of this construction was invulnerable. Indeed, so 
confident were all in this method of applying iron for defence, that 
it was proposed still further to reduce the sectional area of the bars, 
and to substitute wrought-iron supports for the masonry. Two embra¬ 
sures were therefore constructed for experiment, one of bars 10 x 4f-in., 
supported by wrought-iron uprights 2J ft. apart, and every fourth bar secured 
by a dovetail at the back to the upright. The other embrasure was com¬ 
posed of bars 8 x 3|-in., supported at the ends by masonry, and in the centre 
by wrought-iron uprights ft. apart similar to the other. At this experi¬ 
ment, Sir W. Armstrong’s 120-pr. shunt gun was used, and the effect of this 
formidable piece of ordnance against the embrasures was such as to put 
an end at once to all idea of their impenetrability, and the strength anti¬ 
cipated by the wrought-iron supports. It was found that the tongue on the 
bars was readily stripped off, and the uprights broken in the vicinity of the 
blow, leaving, as it were, each bar singly to resist the impact of the shot 
without deriving any support from the others. In the bars used at this 
experiment sufficient care had not been taken in the “ piling " to obtain 
the greatest amount of strength, but independently of this defect in manu¬ 
facture, the very small comparative resistance offered to the shot caused all 
idea of using these bars to be most reluctantly abandoned. Bars of this 
description possess many advantages over wrought-iron plates, if it were 
possible to hold them securely together, and make each one derive its 
proper share of support from the others. The advantages alluded to are as 
follows:—* 
(1) The rapidity with which they can be manufactured. 
(2) The facility of transporting them from the forge to the work. 
(3) The great thickness of metal obtained sound at a comparatively 
small cost per ton, for it must be remembered that the price per ton of 
wrought-iron increases very rapidly in proportion to the weight: for example, 
while £19 per ton was paid for Thorneycroft's bars, with a prospect of a 
very considerable reduction, the armour plates were costing from £32 to 
£40 per ton, and the stern port of the “ Warrior" cost no less than £150 
per ton. 
