Chemistry and Physics. 105 
and the less foreign substances (silicium, sulphur, phosphorus) it con- 
the hardness and tenacity of the steel increase with the amount of t 
bon. From 1] 5 per cent. appears to be the limit at which 
carbon. ‘41 
steel exhibits after hardening the greatest hardness with the greatest 
amounts ‘4o 2:25 or 2:3 per cent. If, therefore, a line of demarca- 
tion were to be drawn between steel and pig iron, which should be 
_ upon the combining proportions, 2°3 would characterize this 
imit. 
on resulted more or less slowly, 
re or less carbon in the combined 
with the iron, and is not separated as graphite. =~ 
wit i process is purely empirical, the eye of 
‘cht and balance in determining the amount 
_ of carbon in the material to be employed. ‘To manufacture cast steel 
_ With certain properties, those materials must be selected in which the 
‘amount of carbon is known, and which, by being fused together in ac- 
i roduce a cast steel containing that 
ds with the properties required of 
d, it was found that it origi- 
ome time in a stoneware 
