235 
ON THE TREATMENT OF MELTED.CAST IRON, 
AND ITS CONVERSION INTO IRON AND 
Selo BY 1HE PNEUMATIC ,.PROCESS: 
BY R. MUSHET. 
N the year 1815, the late Mr. David Mushet, took out 
a patent for the manufacture of refined iron, direct 
from the blast furnace. For this purpose, he erected a 
small blast furnace thirty feet high, blown by means of 
three tuyeres, with a pressure of blast about 34 pounds 
per square inch. These tuyeres wefe arranged so as to dip 
down upon the surface of the melted iron in the hearth of 
the furnace, and when the hearth was full, or nearly full, 
the tuyeres were partially below the surface level of the 
melted iron. There was no difficulty experienced in keep- 
ing the melted iron in a liquid state in the middle of the 
hearth, but round the sides the refined iron chilled and 
formed what is technically termed “scull,’ and this 
rendered it very difficult, and sometimes impossible to tap 
the furnace, and run off the portion of the metal which re- 
tained its fluidity when the tapping took place, the metal 
issued from the furnace intensely heated, and throwing off 
the most brilliant semtillations. The temperature of the 
metal, like that of ordinary refined iron, was far lighter 
than that of pig iron under the regular working of a blast 
furnace. The pigs of metal obtained were perfectly solid, 
showing, when broken, a dense white steely grain. They 
were so strong as to bend before they broke, and occasion- 
ally they could not be broken at all, though struck by the 
heaviest sledges, wielded by the most powerful men. The 
metal was, in fact, crude cast steel, and when annealed, was 
susceptible of being forged at a low heat to some extent. 
The defect 1n this process was that, as in the refinery, the 
waste of metal was excessive, owing to the surface action 
of the blast upon the melted iron for a prolonged period. 
The difficulty of keeping the hearth open, and of tapping, 
arose merely from the small eye of the furnace and earth, 
and weakness of the blast. The iron was, however, decar- 
bonized so as to bein the condition of crude cast steel, but 
too highly oxygenated to be forged into bars of commercial 
value. The experiment I have described, was, I believe, 
the first practical step taken in the development of the 
Pneumatic process, though it was certainly not undertaken 
