986 IRON 



The diameter of the hearth, the sides of -which were parallel, -was 4'3 feet ; diameter 

 at boshes, 1T3 feet; and at top of furnace, 5*3 foot: the top being covered with ;i 

 moveable cover, -which opens to admit the rlnrg>. 



The temperature of the hot-blast was lower than it ought to bo ; rarely exceeding 

 572 Fahr. The blast is introduced into the furnace by three tuyeres, the diaim-trr 

 of which, and the pressure of blast, being varied according to the nature of the f'n< 1 

 made use of, being from 16 '6 lines in diameter, and 16 lines mercurial pressure up to 

 21 lines diameter, with 22 lines pressure. 



It is found by experience that the peculiar bladed texture of spiegeleisen depends 

 more on the percentage of carbon than of the manganese ; for with very high per- 

 centages of the latter, this crystalline structure is not more, if as much, developed as 

 with low percentages of that metal. This structure is also much better developed ',!' 

 the iron, when tapped, ba covered with slag, so as to allow it to cool more slowly, for 

 which reason it is usual to let a considerable quantity of slag accumulate in the 

 furnace, so as to cover the cast when it is topped out. When the iron is poor in 

 carbon, that portion of the cast which has cooled under the slag is invariably more 

 bladed in texture than when not so covered; but if the iron is very rich in carbon 

 (containing, say, 5 per cent, carbon), but little difference is observable. It is there- 

 fore advisable to let the iron run out of the furnace as quickly as possible, as, if not 

 so done, it frequently happens that the iron does not have the desired bladed texture 

 well developed in it. When the percentage of manganese in the cast iron is large, 

 and the iron is tapped very hot, a strong oxidation, with evolution of flames, i 

 on the surface of the cast, and presents a very curious appearance. 



In these works, in order to get good results, care is taken to work the furnaces 

 slowly, so as to keep the manganiferous ore exposed as long as possible to a powerful 

 reducing action, in order to get as much of the manganese reduced along with the iron 

 as possible ; and for this purpose a strong pressure, very hot blast, and very basic 

 charge, are required. The zone of combustion must not (as occasionally happens in 

 Westphalia) be allowed to rise too high above the tuyeres ; and should this take place, 

 the remedies in general use are, to diminish the pressure of the blast, and use the ore 

 in a finer state of division, and wet it with water.. In Westphalia this is generally 

 attributed to the charcoal or coke being of a worse and more open porous texture than 

 usual. 



Coke is becoming more and more used, and is now alone employed at the Char- 

 lottenhiitte, which produces nearly one-half the spiegeleisen made in the district. 

 All accounts agree that it is much superior to either charcoal or the mixture of char- 

 coal and coke, provided only it be of good quality, and free from sulphur ; and it is 

 stated, when coke is employed, that several per cent, units more of manganese can be 

 got into the spiegeleisen than when the same charge is smelted with charcoal, and, 

 for this reason, it is particularly suited for smelting ores rich in manganese. It is 

 also stated that in this district the attempts to increase the amount of manganese in 

 the spiegeleisen, by manganese ores added to the charge, have not succeeded, and that 

 the manganese in such additions has for the most part gone into the slag. 



The charge at this furnace consists of about rds roasted spathic ores, rd brown 

 haematite, containing manganese, and a portion of the latter being replaced by a brown 

 manganese ore from Nassau, containing 25 per cent. Fe. and 19 to 20 per cent. Mn.. 

 which is now generally used throughout the Ehenish district; with good fiuil, and 

 about 50 per cent, of limestone on the weight of the ore, about of the manganese, or 

 even more, may be reduced. When making spiegeleisen, the furnace produces up to 

 70 tons per day, with a consumption of about 22 cwts. of coke to the ton. 



Spiegeleisen, showing an apparently identical fracture to the eye, may vary 

 immensely in its percentage of manganese, and in practice qach cast or tapping 

 should be assayed for itself. This, however, is not done in the Siegen district, whore, 

 although it is the general custom to regard the spiogei as containing an average 

 of 10 per cent., it will be found in actuality to vary from 7 to 11 per cent, when 

 analysed. 



The following analyses show the chemical composition of spiegeleisen from this 

 district when made with coke : 



Hamm. Hochdahl. 

 Carbon 4-129 5-04 



Silicon 

 Sulphur 

 Copper 

 Manganese 

 Iron . 



0-41 

 0-08 

 0-16 

 7-57 

 8674 



99-528 100-00 



