278 



REPORT — 1889. 



rod state the tensile strength was 59 tons per square inch, with 12 torsions 

 in 8". Crucible carbon steel would stand about the same test, and 

 Swedish Bessemer with high carbon slightly higher in torsion, but lower 

 in tensile strength. 



The material E was readily drawn to No. 20 B.W.G., standing 180 lbs. 

 tensile strength (64 tons per square inch), with 157 torsions in 8". An- 

 nealing lowered the tensile strength to 120 lbs. (about 48 tons per square 

 inch), and slightly increased the torsions to 169 in 8". The wire-makers 

 endeavoured to harden both G rods and E wire both in oil and water, 

 but without success. 



Professor Barrett, of Dublin, has kindly undertaken to determine 

 the electrical properties of the steel wire just mentioned, but the re- 

 sults are not yet completed. About twelve months ago the writer, 

 thinking that silicon might confer upon iron qualities suitable for the 

 manufacture of magnets, sent to Mr. Bottomley, in Sir W. Thomson's 

 laboratory, Glasgow, a forged sample, containing 4-43 per cent, of silicon 

 and '18 per cent, of carbon. 



Diagram 2. 



10 20 JO 40 



M«GNETIZIWG FIELD IN C G S. 



SO 



Diagram by Mr. Bottomle.v, showing magnetic retentiveness and susceptibility 

 of Silicon Steel [4-43 per cent. Si] as compared with ordinary iron and 

 steel. 



The results of Mr. Bottomley 's experiments, as will be seen from 

 Diagram No. 2, were unfavourable. He found that the material had less 

 susceptibility and more retentiveness than good soft iron, and that it had 

 enormously less retentiveness than hard steel suitable for magnet-making. 

 The diagram shows two curves, 'A ' and ' B ' ; ' A ' showing the retentive- 

 ness of the bar, and ' B ' the susceptibility. The dotted curve ' C ' repre- 

 sents what the bar should be if it were suitable for magnet-making, and 

 the dotted curve ' D ' what it would be were it good soft iron. 



Considerable attention having been given to the curious non- magnetic 

 properties of manganese steel, the writer was led to make the approximate 

 tests detailed in Table IV., to see if iron alloyed with other elements than 

 manganese would also lose its magnetic susceptibility. From the list 

 given it will be seen that, practically, manganese is the only exception ; for 



