IRON 



985 



ganese, along with only 2 per cent, of carbon ; such an alloy would be a considerable 

 step in advance, as it would to a great extent overcome the objection to the employment 

 of spiegeleisen, which, from its containing a large percentage (4 to 5) of carbon, is less 

 suited for the production of very soft qualities of Bessemer steel. An alloy of iron 

 and manganese made in Carniola, containing 33 per cent, of manganese, has a granular 

 fracture very unlike spiegeleisen. 



It appears when the quantity of manganese contained in a cast iron exceeds a certain 

 point, that there is a tendency for the carbon to diminish in percentage. Mr. Henderson, 

 of Glasgow, states on this subject: ' It is a well-established fact, that in proportion to 

 the increase of manganese in the alloys with iron, so the carbon decreases, so much so, 

 that when you get to 30 per cent, manganese, the carbon is down to 0'25 or 0*40 per cent.' 



In the Filipstad mining district in Sweden, numerous attempts to produce spiegel- 

 eisen by adding the native oxides of manganese, particularly Hausmannite, which 

 contains 72 per cent, metallic manganese, and occurs abundantly in that district, had 

 failed, the iron so produced not containing more than about 4 per cent, of mangnS, 

 as the excess of that metal was invariably carried off in the blast-furnace slag. We 

 understood that a considerable quantity of Hausmannite had been exported to Sheffield 

 from this part of Sweden in the summer of 1871, for the use of steel manufacturers 

 there. The German manufacture of spiegeleisen, which is by far the largest of all, is 

 principally carried on in the northern part of Nassau, and the southern portion of 

 Westphalia. The ores used for the production of spiegeleisen are found in mineral 

 lodes which traverse the Devonian geological formation on the eastern bank of the 

 Rhine. They are the so-called spathic iron ores, which are carbonates of iron contain- 

 ing variable quantities of carbonate of manganese in intimate combination with one 

 another. They usually contain more or less copper and iron pyrites, with, occasionally, 

 traces of galena and zinc blende, and more frequently a large admixture of quartz, 

 which is picked out as cleanly as possible by hand after the ore has been roasted, 

 when the quartz is more easily distingushed by the eye, since it remains whole whilst 

 the iron has become reddish-brown through oxidation. 



The following analyses show the chemical composition of the ores from three of the 

 principal mines : 



Before being smelted, these ores are roasted in kilns from 18 to 20 feet high, with 

 two grates one above the other ; they are filled with coke (small) and ore, using 8'4 

 cubic feet of the former to 2^ tons of the latter, and lighting the whole from the lower 

 gratfe. The ore in each kiln (about 7 tons) is raked out once a day through an aper- 

 ture made by removing some of the upper grate bars. The object of this roasting, in 

 which the ore loses about one-third its original weight, is to expel the carbonic acid 

 from the ore and convert it into oxide ; it also enables, as before mentioned, the quartz 

 mixed with the ore to be picked out by hand. 



At the Lohe blast-furnace, which belongs to the Coeln-Muesener Company, the fuel 

 employed is either charcoal or coke alone or more often a mixture of both. The 

 charges employed are with charcoal alone, 1,035 Ibs. roasted ore, with 180 Ibs. lime- 

 stone to each cubic feet of charcoal, which is chiefly made from beech and oak woods ; 

 with coke alone, it is 2,197 Ibs. roasted ore, with 602 Ibs. limestone to each 42 cubic 

 feet of coke; and with the mixture of charcoal and coke the charge was 1,233 Ibs. 

 roasted ore, with 360 Ibs. of limestone to each 10 cubic feet of coke, mixed with 20 

 cubic feet of charcoal. As a rule, about 40 such charges would be run down in the 

 24 hours, or a total of about from 1,700 to 1,800 centners per week. 



The dimensions of the blast-furnace are as follow : Total height, 42-4 feet ; height 

 from sole of hearth to tuyeres, 2-1 feet ; height from sole to top of hearth, 4'3 feet ; 

 height from top of hearth to boshes, 9'0 feet; and thence to top of furnace, 28'5 feet. 



