30 



JOURNAL OF THE PLYMOUTH INSTITUTION. 



The following short abstract from the paper read before the 

 British Association will show how completely Mr. Bessemer was 

 aware of the true principle involved in his process, even at that 

 early period of the invention. Speaking of the results of the 

 various furnaces he had used for his early experiments, he says : — 

 ''These results all tended to confirm an entirely new view of the 

 subject, which at that time forced itself on my attention; viz., 

 that I could produce a much more intense heat, without any 

 furnace or fuel, than could be obtained by either of the modifications 

 I had used ; and, consequently, that I should not only avoid the 

 injurious action of mineral fuel on the iron under operation, but 

 that I should at the same time avoid the expense of the fuel." 



Mr. Bessemer does not confine himself in his patents to the 

 use of atmospheric air, but shows that oxygen gas may be used in 

 lieu thereof, or a mixture of oxygen with other gaseous fluids ; or 

 he employs any gaseous fluid or matter, containing or capable of 

 evolving oxygen, for the purposes of his invention ; but he prefers 

 atmospheric air on account of its cheapness and efficiency. Nor 

 need we wonder at this preference, when we remember that about 

 one-fifth of the whole atmosphere is pure oxygen gas, which abounds 

 everywhere on the earth's surface, and is the common property of 

 all mankind in quantities unlimited and free of all taxation, and 

 can be obtained at the required pressure with the necessary ap- 

 paratus at much less expense and inconvenience than that of 

 separating oxygen from nitrates or other costly materials, which 

 must first be purchased, carted, and stored at a much higher cost 

 than the mere forcing of atmospheric air. 



Only the best Hematite irons, as a rule, such as West Cumber- 

 land, Whitehaven, Barrow, and others, can be used for this process, 

 as only carbon and silicon get burnt out by the passage of air 

 through the molten metal, and when these are out the oxygen 

 attacks the iron itself in preference to either the sulphur or phos- 

 phorus, and thus in analysis we find that the percentage of sulphur 

 and phosphorus is slightly higher — very slightly — in the steel than 

 in the pig iron before the blast has been passed thi'ough it. 



The principle, therefore, on which the invention is based, as has 

 been already stated, is the passing upwards of atmospheric air or 

 oxygen gas through the fluid mass above that alone makes it suc- 

 cessful. It is not simply an improvement or alteration in the 

 details of a previously known and established mode of making 



