‘162 On the Principles of Iron and Steel. 
‘proportion ‘to the oxygen prefented to the metal, and its 
‘tendency to quit the caloric to unite with the iron. 
3- Pure malleable iron derives its {trength, tenacity, mal- 
leability, and ductility, by being totally deprived of the 
‘principles which conftitute the cold and hot fhort qualities 
‘of iron. This is effected in. the courfe of rendering it mal- 
leable, either by the attention of the workmen, or from the 
‘proper quality ef the crude iron ufed: its fraéture is gene- 
‘sally clear, confilting of fmall regular dark blue grains; by 
much hammering the iron commonly gains fibre, and is 
‘then of a light blue colour, uncommonly tenacious when 
cold. Fhe excellence of pure malleable iran is alfo mani-— 
fefted by the aftonifhing degree of heat it withftands without 
exhibiting the leaft fign of fufion, or without lofing much 
of its metallic parts by exydation. 
A line of diftinétion ought to be drawn betwixt the iron 
produced with wood-charcoal and pit-coal. As the prefent 
relation of the fimple principles of the metal does not im- 
mediately interfere with that diftinétion, it will more pro- 
perly arrange itfelf along with the obfervations on the various 
modes practifed for rendering iron malleable. 
However varioufly conducted the modes of operation are, 
at different works, and in different countries, to produce 
malleable iron, yet the principle of operation is the fame, 
namely, that by diffipating the carbon and oxygen, con- 
tained'in the crude iron, bar or malleable iron is the refult. 
Furnaces of a multiplicity of fhapes have been erected for 
this purpofe ; but in the moft perfect conducted procefles 
‘hitherto, it has been found, that a heavy lofs of metallic 
parts accompanied the manufacture: 40, 35, te 30 cwt. of 
erude iren have been ufed to fabricate 1 ton of finifhed bars ; 
the quantity ufed always. depending upon its aptnefs to 
‘become malleable, the fkilfulncfs of the workmen, the 
operation adopted, and the quality of the malleable iron 
wifhed to be produced. Thefe obfervations more immedi- 
ately relate to the home manufactures of iron with pit-coal ; 
: “but 
