ON METALS. 293 



had done, compact and free from pores. He accounts for this dif- 

 ference by observing, that the heat necessary to melt copper, cal- 

 cines part of the tin ; and the earthy calcined particles of the tin, 

 being mixed in thf mass of the metal, render it porous; but the 

 composition of tin and copper, nutting with less than half the heat 

 requisite to melt the copper, the tin is not liable to be calcined 

 in the serond melting, as in the first. I am rather disposed to 

 think, that the absence of the pores is to be attributed to the more 

 perfect fuMon of the metal : for I have observed at Sheffield, that 

 the same wi-ight of melted steel will fill the same mould to a greater 

 or less height, according to the degree of fusion the steel has been 

 in ; if it ha> been in a strong heat, and thin fusion, the bar of cast 

 steel will be an inch in thirty. six shorter than when the fusion has 

 been less perfect. Upon breaking one of the bars, which had 

 been made from steel in an imperfect fusion, its inside was full of 

 blebs ; a shorter bar of the same weight and diameter, which had 

 been in a thin fusion, was of a closer texture. Now the mixture of 

 tin a.i ! cupper melts far easier than copper does, and it is likely, 

 on tiiAt account, to be in a thinner fusion when it is cast. 



It may deserve to be remarked, and I shall have no other oppor. 

 tunity of doing it, that the melting or casting of steel was intro- 

 duced at Sheffield, about forty years ago, by one Waller from 

 London ; and was afterwards much practised by one Huntsman, 

 from whom steel so prepared, acquired the name of Huntsman's 

 cast steel. It was first sold for fourteen-pence, but may now be 

 had for ten. pence a pound ; it costs three. pence a pound in being 

 melted, and for drawing ingots of cast steel into bars of the size of 

 razors, they pay only six shillings for a hundred weight, and ten 

 shillings for the same quantity when they make the bars into a size 

 fit for small tiles, &c. The cast steel will not bear more than a red 

 heat ; in a welding heat it runs away under the hammer like sand. 

 Before the art of casting steel was introduced at Sheffield, all the 

 cast steel used in the kingdom was brought from Germany ; the 

 business is carried on at Slufikld with greater advantage than at 

 most other places, for their manufactures furnish them with great 

 abundance of broken tools ; and these bits of old steel they pur* 

 chase at a penny a pound, and melt them, and on that account they 

 can atiord their cast j>t<-el cheaper than where it is made altogether 

 from fresh bars of steel. 



