ON THE INFLUENCE OF SILICON ON THE PROPERTIES OF STEEL. 47 



Substances. Eelative 



hardness. 



Apatite 34 



Hard cast-iron scrap 36 



Window glass 60 



Good razor steel fiO 



Very hard white iron 72 



The following are the general conclusiona arrived at from this series 

 of experiments. On adding silicon, in the form of silicon pig, to the 

 purest Bessemer iron, the following results are obtained : — 



The metal is quiet in the mould when even a few hundredths per 

 cent, of silicon are added. The metal is originally red short, especially at 

 a dull red heat, though it works well at a welding temperature ; the red 

 shortness is increased by silicon. In all cases examined, the metal was 

 tough cold, and welded well, silicon having little or no influence. Silicon 

 increases the elastic limit and tensile strength, but diminishes the elono-a- 

 tion and the contraction of area, a few hundredths per cent, havino- a 

 remarkable influence in this respect. The appearance on fracture by 

 tensile force is changed from finely silky to crystalline, while the fracture 

 produced by a blow gradually becomes more like that of tool steel as 

 silicon increases. The hardness increases with the increase of silicon, but 

 appears to be closely connected with the tenacity. With 0-4! per cent, of 

 silicon and 0'2 per cent, of carbon, a steel was obtained diSicnlt to woi'k 

 at high temperatures, but tough when cold, capable of being hardened in 

 water, and giving a cutting edge which successfully resisted considerable 

 hard usage. In some cases silicon was present in the oxidised condition • 

 the efiect is then very diS'erent, and the mechanical properties of the 

 metal more nearly resemble those of the original Bessemer iron. 



In the second series of experiments various proportions of silicon have 

 been added to ingot metal, containing manganese and carbon, as ordina- 

 rily met with in commerce. The results are not yet quite ready for 

 publication, but they show that manganese greatly modifies the effect of 

 silicon in producing x'ed shortness, and hence enables the metal to be 

 readily rolled and otherwise worked, even in presence of several tenths 

 per cent, of silicon. The low extension, however, though not nearly so 

 marked as before, is still observed, despite the presence of manganese • and 

 hence, for the majority of the applications of mild steel, silicon does not 

 appear to be advantageous. 



Third Report of the Committee, consisting of Professor Gr. Forbes 

 {Secretary), Captain Abney, Dr. J. Hopkinson, Professor W. G. 

 Adams, Professor G. C. Foster, Lord Eayleigh, Mr. Preece, 

 Professor Schuster, Professor Dewae, Mr. A. Vernon Harcourt, 

 Professor Ayrton, Sir James Douglass, and Mr. H. B. Dixon 

 appointed for the purpose of reporting on Standards of Light. 



The Committee have been anxious during the past year to carry out com- 

 parative experiments on the various standards of light hitherto proposed, 

 but have been prevented by want of funds from doing much. Professor 

 W. G. Adams, however, has presented a report to the Committee ou pre- 



