178 ANNUAL OF SCIENTIFIC DISCOVERT. 



peatedly made use of for more than 30 years in the commonest 

 practice of Europe and America. The differences, which are 

 many and great, are all mechanical, and the Bessemer process 

 may, with strict accuracy, be said to be the employment of entirely 

 new mechanical methods and appliances for effecting old and familiar 

 reactions. 



" The gist of the Bessemer process lies in this : that the metal 

 is kept fluid from the beginning to the end, from the time 

 when the metal is first touched by the oxygen, until it is finally 

 cast into workable and definite shape in the ingot moulds. This 

 implies an enormous increase of heat during the working, for 

 wrought iron is very difficultly fusible in the most intense heat 

 of the blast furnace, and not at all so in the reverberatory fur- 

 nace. But in this method, not only is the purified wrought iron 

 melted to a state of extreme fluidity, but it retains a surplus of 

 heat sufficient to keep it liquid for a considerable time after it has 

 received an admixture of 5 to 10 per cent, of cast iron at less than 

 half its temperature, and it can still be poured in a thin stream, 

 and cast with facility. Indeed, no other process known to the 

 arts develops a degree of heat at all comparable to this, and the 

 most surprising thing connected with it is the simple and unex- 

 pected means by which it is obtained." 



The cast iron intended for conversion must be as free as possi- 

 ble from sulphur and phosphorus, since in this process the sul- 

 phur is removed with difficulty, and the phosphorus, practically, 

 not at all. The metal is first melted in a cupola furnace, whence 

 it is run into the " converter " which receives the charge (12,000 

 pounds) in a horizontal position, in order that the metal may not 

 run into the tuyere-holes in the bottom. When charged the blast 

 is let on and the vessel righted. The action commences im- 

 mediately. 



*'Asin the puddling furnace, the first change is in the oxida- 

 tion of iron and silicon. The silicon becomes silicic acid, and 

 enough of the iron oxidizes to satisfy the affinities of the acid, and 

 does not decompose during the remainder of the blast. It is 

 cluring this stage of the process that the remarkable heat of the 

 conversion is developed. It will be remembered that when sili- 

 con oxidizes it takes up 3 equivalents of oxygen. Carbon takes 

 up only 1 in this process, becoming carbonic oxide. It is a 

 common error to suppose that any very great quantity of heat is 

 generated by the combustion of the carbon, that is, as com- 

 pared with that derived from the silicon. The heat generated by 

 the silicon burning to silicic acid will be found by the ap- 

 plication of the coefficients and formuke of the mechanical the- 

 ory of heat to be from 2 times to 3 times greater than that 

 generated by the burning of the carbon to carbonic oxide. 

 Another circumstance of importance is that the silicic acid re- 

 mains as a dense fluid in the converter, no part of its heat being 

 lost, except such as is carried out of the converter by the atmos- 

 pheric nitrogen, and none is rendered latent by converting it into 

 vapor; while the carbon is vaporized, a physical change. absorb- 

 ing much heat, and the vapor thus formed is carried out of the 



