74 
POPULAR SCIENCE REVIEW. 
Experience appears to liave modified the conditions. All 
varieties of iron are not advantageously treated by the Bessemer 
process; but some varieties, such as the Swedish irons and 
some of the very best British pigs, are now being converted 
into that valuable metal, existing in a state between iron and 
steel, employed for plating those ships of war which are to 
withstand the hammer-headed shots projected from an Arm- 
strong gun. From a metal similar to this are made those 
remarkable pieces of Ordnance manufactured by Whitworth. 
There appears to be a stage in the process of converting iron 
when we have all the qualities of the best steel, combined with 
the valuable properties of malleable iron. This condition is 
arrived at by another process. Articles of various kinds, such 
as screws, pulleys, &c., requiring great toughness, are cast from 
the ordinary selected pig. In this state they are very hard, and 
consequently very brittle. These articles are placed in a furnace 
with a quantity of hematite iron ore, and the whole exposed 
for some tune to a moderately high temperature. The per- 
oxide of Aon, under the action of heat, removes a certain 
portion of the carbon, and exceeding toughness results from the 
operation. Stirrups, bits, spurs, and much saddlers’ iron- 
mongery, are now made by this process. Although this opera- 
tion has in many respects the character of annealing, yet it is 
something more. It is quite certain that a molecular change 
takes place by the long- continued action of heat alone ; beyond 
this, however, the presence of the peroxide of iron determines 
by chemical action the constitution of the metal. Veiy fine 
castings, many of them copies of examples of high art, are 
made by this process. A very liquid metal is obtained to secure 
the requisite sharpness. This would be brittle when cold ; but 
by the combined action of heat and hematite, the requisite 
toughness is secured. 
Before leaving this portion of our subject, the Berlin iron- 
castings claim some attention. Dumas has stated that these 
remarkably delicate productions are due to the presence of 
phosphorus and arsenic in the iron from which they are cast. 
These substances certainly have a tendency to give great 
fluidity to the melted iron, and fluidity is essential to the pro- 
duction of such filigree-work as we see in the elaborate brace- 
lets, neck-chains, brooches, and fans which many of the Berlin 
foundries produce. 
The reputed origin of this manufacture is interesting. At 
the time when the final struggle commenced between Prussia 
and Napoleon, the patriotism of the Prussian ladies was particu- 
larly conspicuous. They sent their jewels and trinkets to the 
R-oyal Treasury to assist in furnishing funds for the expenses of 
the campaign. Rings, crosses, and other ornaments in cast-iron 
