Chap. 29.] Smelting of Iron. 16$ 



Nature like wife prefents iron in a faline ftate, united 

 to the vitriolic acid, and forming green vitriol. This 

 fait is particularly found in mines which contain py- 

 rites. Iron is offceh found united to fulphur, and 

 then forms what are called martial pyrites. This 

 metal is alfo found combined with arfenic, both 

 being in the metallic ftate. There is alfo a blacfc 

 iron ore, which is in fome meafure attracted by 

 the magnet. Iron is fometimes found in the form 

 of a blue powder. In this ftate it is called native 

 Pruflian blue. It is mixed with vegetable earths, and 

 .cfpecially with turf. It was difcovered fome years ago, 

 that iron is often united with the phofphoric acid. The 

 muddy .or bog ores are fometimes of this nature. 



The ores of iron do not afford the metal unlefs urged 

 by a great heat. Some ores are melted without addi- 

 tion ; but it is necefiary to afiift the fufion of others by- 

 calcareous matters. The limeftones, the iron ore, and 

 charcoal, are alternately thrown into the furnace, and 

 the whole is covered with a layer of charcoal. The 

 melted ore is reduced by the contact of the coaly 

 matter, and is then fuffered to run into a cavity ufually 

 formed in fand. The metal in this ftate is called crude 

 or caft iron. A vitreous matter, called flag, paiTe$ 

 after the iron, and confifts of the ftones which were 

 added to facilitate the fufion. The metal thus ob- 

 ^ftined has not the leaft duftility; but it is deemed 

 better in proportion as its colour is darker. 



The caft iron is carried to be refined in a forge 

 furnace, with a hollow hearth, in which it is furrounded 

 with charcoal, where the fire is urged by bellows till 

 the metal begins to foften. When it is in this ftate, 

 it is repeatedly ftirred, in order that it may prefent a 

 larger furface to the air. By the adion of the heac 

 and air it emits fparks, which proceed from the con- 

 fumption of a quantity of plumbago, or black lead 

 M 2 which 



