"The contradictory testimony concerning the effect of silicon on steel has been well summarized by Mr. Howe,2 who records many examples of exceptional steels with

1 Campbell, "Manufacture and Properties of Structural Steel."

2 "The Metallurgy of Steel." abnormal contents of silicon, and who fully discusses the theories advanced by different writers.

"He finds no proof that silicon has any bad effect upon the ductility or toughness of steel, and he concludes that the bad quality of certain specimens is not necessarily due to the silicon content, but to other unknown conditions."

In discussing the results of the investigation of Mr. Hadfield,1 the following remarks are made by Mr. Campbell: "These results are of the highest value in showing that silicon cannot be classed among the highly injurious elements, for in similar proportion (the percentages of silicon in the investigations in question range from 0.21 to 5.08) phosphorus and sulphur would be out of the question, manganese would give a worthless metal, and carbon would change the bar to pig-iron. It will, therefore, be only reasonable to suppose that small quantities cannot exert a very deleterious influence."

Finally, the same author remarks that "in steels containing less than 0.25 per cent, of carbon, the effect of small proportions of silicon upon the ultimate strength is inappreciable."