583 
Cast Iron^ Steely and Malleable Iron, 
rating with the carbon of the iron, carbonic oxide gas, as well 
as carbonic acid ; and the evolution of these gases causes the 
well-known ebullition of the whole mass. In this separated 
state of the molecules, it is very difficult for heat to be brought 
to act on them ; and it is, in fact, well known to all workmen, 
that several metals are the more difficult to re-melt the more 
minute their state of division. 
Each grain of the iron, not being in a fluid state, by losing 
the carbon, silicon, &c., is converted into the base of malle- 
able iron, leaving behind only a skeleton of the grains of 
cast iron. All the crystalline planes are destroyed ; and 
therefore, instead of the crystals adhering to each other with 
their planes of crystallization by a force easily to be over- 
come, an innumerable quantity of points of the skeleton of the 
crystals adhere together in all directions of the adhesive 
force ; and as we have before observed, that the skeleton 
grains are naturally not in a liquid state, the spaces formerly 
occupied by the carbon, silicon, and portions of iron, which 
have been consumed, are still vacant, consequently the iron 
in this state exerts a very great decomposing power upon 
all chemical bodies, as is the case with oxide of iron reduced 
at a low degree of heat by hydrogen. This fact likewise ex- 
plains the circumstance, which I have often observed, that by 
using bad coals, or when the draught of the furnace is not 
well regulated, the iron which during the first half of the 
process of puddling had lost all its sulphur by chemical 
means, exhibited at the end of the process more sulphur than 
the cast iron actually contained before the puddling com- 
menced. 
The vacant spaces in the skeleton grains which constitute 
the lumps of iron made in the puddling furnaces, are imme- 
diately closed when brought under the forge hammer, and 
consequently the decomposing power ceases ; but where the 
malleable iron thus obtained is again kept at a white heat for 
a considerable space of time, the closed pores in some mea- 
sure re-open, and their attractive force towards chemical 
agents begins to re-appear, and thus, to mention one in- 
stance, the iron combines in the cementing furnace wdth car- 
bon, forming cemented steely without altering the juxta-position 
of the silicon and iron molecules in the cemented bar. Such 
a cemented bar, when exposed to a proper degree of heat, 
will weld to another similar bar, as the mechanical texture of 
the iron had not been altered. But it is different when the 
cemented steel, instead of being softened only, is reduced to a 
perfect liquid state by melting. In this case the iron and si- 
and I used a similar apparatus, for ascertaining the nature of the escaping 
gases, after the boiling mass had been mixed with different chemical agents, 
