Fossils. in 



sure to air, it soon turns black and dull. 

 Its specific gravity is 8,310; its hardness 

 is somewhat considerable, and seemingly 

 surpassing that of copper. But its duc- 

 tility is so little, and its brittleness so great 

 that it is readily converted into powder by 

 the hammer. 



Of all metals Iron exhibits the most 

 varieties and deviations. Its differences 

 in colour, density, fracture, tenacity, duc- 

 tility, and degree of fusibility, are uncom- 

 monly great. Soft and malleable iron has 

 a greyish-white^ colour, a light grey, fi- 

 brous,hackly fracture. Its specific gravity 

 at a mean rate is 7,700 ; its hardness is 

 not great, but its malleability and tenaci- 

 ty are considerably so ; and it has this 

 characteristic property, not possessed by 

 other species of this metal, that whether 

 cold or ignited, it may be extended, forg- 

 ed, and bent, without breaking. 



By cast or crude iron, that metal is 

 understood, which is obtained by the 

 first smelting of iron-ores. Such iron is 

 distinguished from ductile iron by its re- 

 fusing to be extended and forged by the 

 hammer, whether cold or ignited, by its 

 brittleness ,aud by its fusing in strong heat 



