198 
MINUTES OE PROCEEDINGS OF 
capable of receiving very different degrees of hardness by tempering, even so as to 
cut wrought-iron with facility, and fusible in furnaces; and lastly, when present in 
greater proportion than in steel, we have cad-iron, which is hard, comparatively 
brittle and readily fusible, but not forgeable or weldable. The differences between 
these three well-known sorts of iron essentially depend upon differences in the 
proportion of carbon, . 
"With regard to the modes of effecting the combination of carbon with iron. 
Dr Percy states: 
“ The essential condition of this combination is, contact of iron at, or above, a red 
heat with carbon, or with certain gaseous compounds of carbon. When an oxide of 
iron is reduced in admixture with excess of carbon, at or above the melting point* 
of cast-iron, combination takes place rapidly and cast-iron is produced. 
But combination is also effected, though much more slowly, when iron in the 
compact state of bar imbedded in charcoal powder is exposed to any temperature at 
or above redness.f In this way steel is very largely made in England, . 
[Relative to the per centage of carbon which distinguishes steel from 
cast-iron. Dr Percy quotes the opinion of Karsten, the German, who states, 
“.in all iron containing more than from 0*2 to O'25 of carbon the 
metal is designated steel .and 2' of carbon appears to be the limit between 
steel and cast-iron.” 
In speaking of the conversion of cast-iron into malleable or wrought-iron 
by puddling, Dr Percy says : 
“ This process consists essentially in stirring about pig-iron molten on the bed 
of a reverberatory furnace, heated by flame, until it becomes converted into 
malleable iron, through the decarburizing action of the oxygen of the ah.” 
Three main points have been proposed for consideration in the 
ments which have been carried on, viz.:— 
(1) To determine material. 
(2) To determine form. 
(3) To endeavour to obtain a shell which would act effectively 
armour-clad vessels. 
I propose to show the decision which has been arrived at under each of 
these heads. 
Service Cast-iron Shot. 
In October, 1858, an experiment was made at Portsmouth, to determine 
the comparative effect of 68-pr. and 32-pr. cast-iron shot, and also the effect 
of such shot at 20 yds. range, against iron plates. 
The shot were fired at wrought-iron plates 4 in. thick, fastened to a ship's 
side; the following results were obtained:—■ 
32-Pounder. 
At 400 yds. Made an indent of 1*25". 
At 100 yds. Mean of six rounds, an indent of 2'16". 
At 20 yds. Penetrated the plate. 
experi- 
against 
* 2786° Eah. 
f 1830°. 
