258 ANNUAL OF SCIENTIFIC DISCOVERY. 



required capable of compressing air to about Slbs. or lOlbs. to the square 

 inch. 



" A communication having been made between it and the tuyeres before 

 named, the converting vessel will be in a condition to commence work ; it 

 will, however, on the occasion of its first being used after re-lining with fire- 

 bricks, be necessaiy to make a fire in the interior with a few baskets of coke 

 so as to dry the brick work, and heat up the vessel for the first operation, 

 after which the fire is to be all carefully raked out at the tapping hole, which 

 is again to be made good with loam. The vessel will then be in readiness to 

 commence work, and may be so continued without any use of fuel until the 

 brick lining in the course of time becomes worn away and a new lining is 

 required. I have before mentioned that the tuyeres are situated nearly close 

 to the bottom of the vessel; the fluid metal will therefore rise some eighteen 

 inches or two feet above them. It is therefore necessary, in order to prevent 

 the metal from entering the tuyere holes, to turn on the blast before allowing 

 the fluid crude iron to run into the vessel from the blast furnace. This hav- 

 ing been done, and the fluid iron run in, a rapid boiling up of the metal will 

 be heard going on within the vessel, the metal being tossed violently about 

 and dashed from side to side, shaking the vessel by the force with which it 

 moves, from the throat of the converting vessel. Flame will then immedi- 

 ately issue, accompanied by a few bright sparks. This state of things will 

 continue for about fifteen or twenty minutes, during which time the oxygen 

 in the atmospheric air combines with the carbon contained in the iron, pro- 

 ducing carbonic acid gas, and at the same time evolving a powerful heat. 

 Now, as this heat is generated in the interior of, and is diffusive in innumera- 

 ble fiery bubbles through, the whole fluid mass, the metal absorbs the greater 

 part of it. and its temperature becomes immensely increased, and by the 

 expiration of the fifteen or twenty minutes before named that part of the 

 carbon which appears mechanically mixed and diffused through the crude 

 iron has been entirely consumed. The temperature, however, is so high that 

 the chemically combined carbon now begins to separate from the metal, as is 

 at once indicated by an immense increase in the volume of flame rushing out 

 of the throat of the vessel. The metal in the vessel- now rises several inches 

 above its natural level, and a light frothy slag makes its appearance, and is 

 thrown out in large foam-like masses. This violent eruption of cinder gene- 

 rally lasts about five or six minutes, when all further appearance of it ceases, 

 a steady and powerful flame replacing the shower of sparks and cinder which 

 always accompanies the boil. The rapid union of carbon and oxygen which 

 thus takes place adds still further to the temperature of the metal, while the 

 diminished quantity of carbon present allows a part of the oxygen to combine 

 with the iron, which undergoes combustion and is converted into an oxide- 

 At the excessive temperature that the metal has now acquired the oxide as 

 soon as formed undergoes fusion, and forms a powerful solvent of those earthy 

 bases that are associated with the iron. The violent ebullition which is 

 going on mixes most intimately the scoria and metal, every part of which is 

 thus brought in contact with the fluid oxide, which will thus w r ash and 

 cleanse the metal most thoroughly from the silica and other earthy bases 



