Report on the Progress and State of Applied Mechanics. 211 



18. Neverfclieless some inventions have been carried into effect, whose 

 tendency is to improve the quality of iron by increasing its strength, 

 such as the smelting of iron by coke deprived of sulphur by the process 

 of Mr. Calvert, whereby one of the most weakening impurities is re- 

 moved, — and the mixing of wrought iron with cast iron, to produce a 

 metal tougher than ordinary cast iron, invented by Mr. Morries Stirling. 

 The effect of repeated meltings on the strength of cast iron, has been tested 

 by Mr. Fairbairn, who found the iron increased both in tenacity and in 

 hardness, by each melting up to the twelfth ; while, for meltings beyond 

 the twelfth, the iron, though its hardness is increased, becomes brittle. 



19. The process of Mr. Bessemer, for puddling iron by a blast of air, 

 although it has been found to answer perfectly with the iron of Nova 

 Scotia, has not hitherto succeeded with that of Scotland and of Stafford- 

 shire ; and until further experiments have been made, it is impossible to 

 state what its results in most cases may be. 



20. One of the greatest improvements ever made in the manufacture 

 of Steel, was that effected by the use of carburet of manganese, or of 

 cai'bon and manganese separately added : a source of immense benefit to 

 all manufacturers and users of steel, — but of ruin to its inventor, the 

 late Mr. Heath. 



21. Various improvements, too numerous to mention in detail, have 

 of late years been made in converting iron into steel, case-hardening, 

 moulding, casting, shingling, rolling, forging, welding, rivetting, and 

 other processes applicable to cast and wrought iron, and to steel. An 

 important instrument in those improvements which relate to the manu- 

 facture and forging of wrought iron, has been the steam hammer : 

 whether the original steam hammer of Nasmyth, in which the hammer 

 is attached to the piston, or the later steam hammer of Condie, in which 

 the piston is fixed and the cylinder carries the hammer. It is by such 

 an implement alone that such forgings can be executed as the engine, 

 paddle, and screw-shafts of the Great Eastern. 



22. Next to iron in abundance and utility, and also in strength, is 

 COPPER ; along with which may be considered its alloy wiih zinc, the 

 ordinary Irrass, and witli tin, also known as brass, but more properly 

 called bronr.e, and classed, according to the proportion of its constitu- 

 ents, into gun-metal, bell-metal, and speculum-metal ; the first, which 

 contains most copper, being the softest and toughest ; and the last, 

 which contains most tin, being as brittle as glass. Modern chemistry 

 has shown the necessity of combining the constituents of each of those 

 alloys in atomic pro27oriio')is, in order that the compound metal pro- 

 duced may be uniform in structure, and free from flaws, and that 

 according to its purposes, it may be strong, sonorous, or brilliant. 



