Chemistry and Physics. 



407 



Mr. Bessemer has devoted his attention almost exclusively to the subject, 

 Preliminary trials were made on from ten to twenty pounds of iron, and 

 " although the process was fraught with considerable difficulty, it exhib- 

 ited such unmistakeable signs of success," Mr. Bessemer observed, " as to 

 induce me at once to put up an apparatus, capable of converting about 

 seven hundred of crude pig iron into malleable iron in thirty minutes." 



" I set out with the assumption that crude iron contains about five per 

 cent, of carbon ; that carbon cannot exist at a white heat in the presence 

 of oxygen without uniting therewith and producing combustion; that 

 such combustion would proceed with a rapidity dependent on the amount 

 of surface of carbon exposed : and, lastly, that the temperature which 

 the metal would acquire would be also dependent on the rapidity with 

 which the oxygen and carbon were made to combine, and consequently 

 that it was only necessary to bring the oxygen and carbon together in 

 such a manner that a vast surface should be exposed to their mutual ac- 

 tion, in order to produce a temperature hitherto unattainable in our largest 

 furnaces. , 



With a view of testing practically this theory, I constructed a cylin- 

 drical vessel of three feet in diameter and five feet in height, somewhat 

 like an ordinary cupola furnace, the interior of which is lined with fire 

 bricks ; and at about two inches from the bottom of it I insert five tuyere 

 pipes, the nozzles of which are formed of well-burned fire clay, the orifice 

 of each tuyere being about three-eights of an inch in diameter ; they are 

 so put into the brick lining (from the outer side) as to admit of their 

 removal and renewal in a few minutes when they are worn out. At one 

 side of the vessel, about half way up from the bottom, there is a hole 

 made for running in the crude metal, and on the opposite side there is a 

 tap-hole stopped with loam, by means of which the iron is run out at the 

 end of the process. In practice this converting vessel may be made of 

 any convenient size, but I prefer that it should not hold less than one, 

 or more than five tons, of fluid iron at each charge. The vessel should 

 be placed so near to the discharge hole of the blast furnace as to allow 

 the iron to flow along a gutter into it ; a small blast cylinder will be re- 

 quired capable of compressing air to about 8lb. or 101b. 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 relining with 

 fire-bricks, be necessary to make a fire in the interior with a few baskets 

 of coke, so as to dry the brickwork, and heat up the vessel for the first 

 operation, after which the fire is to be all carefully raked out at the tap- 

 ping-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, with- 

 out 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 having been done, 

 and the fluid iron run in, a rapid boiling up of the metal will be heard 



