396 



SCIENTIFIC RECREATIONS. 



rendered us the greatest service, and placed us at the head of nations. 

 It occurs native in meteoric stones. 



. Iron is obtained from certain ores in England and Sweden, and these 

 contain oxygen and iron (see Mineralogy). We have thus to drive away 

 the former to obtain the latter. This is done by putting the ores in small 

 pieces into a blast furnace (fig. 402) mixed with limestone and coal. The 

 process of severing the metal from its ores is termed smelting, the air 

 supplied to the furnace being warmed, and termed the " hot blast." The 

 " cold blast " is sometimes used. The ores when dug from the mine are 

 generally stamped into powder, then " roasted," that is, made hot, and kept 



so for some time to drive off water, 

 sulphur, or arsenic, which would pre- 

 vent the " fluxes " acting properly. 

 The fluxes are substances which will 

 mix with, melt, and separate the 

 matters to be got rid of, the chief 

 being charcoal, coke, and limestone. 

 The ore is then mixed with the flux, 

 and the whole raised to a great 

 heat; as the metal is separated it 

 melts, runs to the bottom of the 

 " smelting furnace," and is drawn off 

 into moulds made of sand ; it is 

 thus cast into short thick bars called 

 " pigs," so we hear of pig-iron, and 

 pig-lead. Iron is smelted from 

 "ironstone," which is mixed with, 

 coke and limestone. The heat re- 

 quired to smelt iron is so very great, 

 that a steam-engine is now generally 

 employed to blow the furnace. 

 (Before the invention of the steam- 

 engine, water-mills were used for the 

 same purpose.) The smelting is 

 Fig. 4 o 2 .-B!ast fumace. conducted in what Is called a blast 



furnace. When the metal has all been " reduced," or melted, and run down 

 to the bottom of the furnace, a hole is made, out of which it runs into the 

 moulds ; this is called " tapping the furnace." 



Smelting is often confounded with melting, as the names are some- 

 what alike, but the processes are entirely different ; in melting, the metal is 

 simply liquefied, in smelting, the metal has to be produced from ores which 

 often have no appearance of containing any, as in the case of iron-stone, 

 which looks like brown clay. 



The cone of the furnace, A, is lined with fire-bricks, ii, which is encased 

 by a lining, //; outside are more fire-bricks, and then masonry, ;// n ; 



