"Steel may contain up to 1 per cent, of copper without being seriously affected, but if at the same time the sulphur is high, say 0.08 to 0.10 per cent., the cumulative effect is too great for molecular cohesion at high temperatures, and it cracks in rolling. This tearing occurs almost entirely in the first passes of the ingot, so that it is of little importance to the engineer, who is concerned only with perfect finished material. In the purest of soft steels, containing not more than 0.04 per cent, of either phosphorus or sulphur, the influence of even 0.10 per cent. of copper may be detected in the less ready welding of seams during the process of rolling; but ordinarily, when the sulphur is below 0.05 per cent., the copper injures the rolling quality very little, even if present in the proportion of 0.75 per cent. In all cases the cold properties seem to be entirely unaffected.

"These conclusions are not founded on any limited series of tests or special alloys; they are the fruit of years of experience in the making of millions of tons of cupriferous steels, and it is quite certain that any baneful influence of this constant companion would have been felt in the many investigations which have been made into the mechanical equation of structural metal."