THE ROYAL ARTILLERY INSTITUTION. 
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sterner stuff/ 1 for instance our B.L. guns are all of wrought-iron, but we 
line our heavier Woolwich guns with toughened steel, and if we make rifled 
1000-prs. we shall have to insert a platinum chamber or, which is much 
more feasible, use “ pellet ” powder. 
Materials for rifled ordnance . 
Economy limits our considerations of the metals as materials for rifled 
ordnance to bronze, wrought-iron, cast-iron, and steel. 
Bronze has several of the properties which are valuable in a gun material, 
but its liability to become hot and soft by repeated firing makes it still 
more objectionable for rifled guns than for smooth-bores, as the edges of 
the grooves would soon be worn away by abrasion from the studs. ''Bronze, 
however, answers pretty well for small guns, and we have made a battery or 
two of bronze rifled mountain guns, and a couple of field guns have been 
made for experiment. 
The Austrians made some mountain guns of sterro-metal, which is an 
alloy of copper and zinc with small quantities of iron and tin added. This 
metal was tested in the Arsenal in 1863. It was proved to possess great 
strength, elasticity, and hardness, but to be more brittle and more subject 
to corrosion than gun-metal.* 
Cast-iron is the first result of extracting iron from the ore. It therefore 
contains many foreign elements, the principal of which are carbon and 
sulphur with which it is infected by the fuel with which it is smelted, and 
phosphorus, silicon, and manganese, which it generally inherits from its 
mother earth. 
Cast-iron contains from 2 to 5 per cent by weight of carbon, existing in 
two forms chemically combined, and mechanically combined. It is carbon 
in the latter state, or graphite, which gives the iron its grey or mottled 
appearance whilst iron with which all the carbon is chemically combined is 
called white iron or bright iron. 
The whiter the iron the harder it is, the greyer the more tenacious. 
Hence mottled iron is the most suitable for guns and white iron for 
projectiles intended to pierce armour plates. Chilled iron is white iron 
artificially produced by cooling the molten metal so rapidly in iron moulds 
that graphite has no time to form. 
*5 per cent by weight of phosphorus makes iron brittle, when cold (" cold 
short”), whilst a much smaller proportion of sulphur renders it brittle 
when hot (“ red* short ”). 
Hence it is that cast-iron, possessing so many impurities in different 
degrees, is weak and brittle and, at all events, uncertain in its nature, and 
therefore not trustworthy as a wholesale material for rifled guns. 
Wrought-iron and steel are simply cast-iron purified (by the processes of 
refining, puddling, &c.) from almost the whole of the foreign elements 
except carbon and perhaps a little sulphur and phosphorus* but it is carbon 
which is the essential difference between cast-iron* wrought-iron* and steel. 
* Extracts Ltom O.S; Committee Proceedings, Yol. I. p. 210. 
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