76 ANNUAL OF SCIENTIFIC DISCOVERY. 



capable of great extension, which must in a great degree be determined by 

 the available means of transport, and the facility with which the ore can be 

 brought .in proximity with the fuel. 



He next proceeds to an examination of the various processes adopted in 

 the manufacture of iron and to their susceptibility of improvement. Mr. 

 Blackwell says that the differences in chemical nature of the various elements 

 forming, on the one hand vegetable, and on the other mineral fuel, are only 

 hi degree, and not in kind, except in so far as regards the composition of the 

 earthy residuum of ashes left after the volatilization of the other elements. It 

 may therefore be in the different nature of the substances present in the ashes 

 of wood and of coal that we must seek for the explanation of the causes 

 which produce such a widely different quality in iron smelted with these two 

 species of fuel. He considers that sufficient attention has not been hitherto 

 paid to this subject, or to the mechanical operations by which a large part of 

 the earthy impurities of all coal seams of a caking nature, might be separated 

 from them before they are converted into coke. Again, he says that, not- 

 withstanding the great extent to which raw coal and partially torrefied wood 

 have been long used in the blast furnaces both in England and abroad, on a 

 careful consideration of the process to which both coal and wood must be 

 subjected before the carbon they contain can be utilized in the reactions of 

 the furnace, it appears that their carbonization may be effected with most 

 economy, and that the quality of the charcoal or coke which results from this 

 process will be best, when effected in close ovens prior to the introduction of 

 the fuel into the blast furnaces, and not within the furnace itself. After 

 pointing out the source of some of the losses sustained by iron masters in 

 England and in South "Wales, especially from imperfect smelting, he remarks 

 that much controversy has taken place with respect to the difference in 

 quality supposed to exist between pig iron smelted with cold and with hot 

 blast. It was generally considered that the pig iron smelted with hot was 

 inferior in quality to that produced with cold air, but he had attributed this 

 impression to ignorance of the facts of the case. Furnaces blown with heated 

 air exerted so great a reducing power, that refractory ores calculated to pro- 

 duce inferior iron were now easily smelted, and thus had arisen the opinion 

 alluded to. At the same time, he admitted that the more elevated tempera- 

 ture of the hot blast furnace had a tendency in a slight degree to increase the 

 quantity of silicium and other cognate metals which formed alloys with pig 

 iron in the smelting process. 



In treating of the operations for converting carbonized crude iron into 

 malleable, he mentioned that at several works on the Continent the attempt 

 to arrest the process of decarburation in the puddling or boiling furnace at 

 that point at which the conversion has proceeded so far as to leave the iron 

 in the state of steel or subcarburet, was believed to have been successful, and 

 that a valuable natural or puddled steel, not requiring cementation before 

 conversion into refined cast or steel, had been the result. He cited as a proof 

 of the faultiness of the present mode of operating, that in some of the largest 

 iron making districts of Great Britain, the production of one ton of inferior 

 wrought iron was only obtained by the consumption of one and one half tons 



