Barrett — On the Magnetic Moment of Steel, etc. 



469 



from 1 to 2 per cent. The magnetic moment, therefore, does not 

 follow the order of hardness in the ingots. 



In some of the ingots a most beautiful quasi-crystalline appear- 

 ance was presented. The molten metal cooling down from the 

 outside of the mould, the needles or fibres of cooler steel started 

 from each cool face, and so arranged themselves geometrically in 



Fig. 2. 



groups at right angles to the four cool surfaces. The appearance 

 is shown at A, fig. 2, engraved from a photograph, of half a link 

 made of manganese steel. The peculiar structure disappears in 

 forging, as is shown in the other end of the link B, which has been 

 forged, and is evenly granular in texture. 



But whilst the molecular structure of the material is an impor- 

 tant factor in determining its magnetic character, there can be little 

 doubt that the extraordinary reduction in magnetic moment pro- 

 duced by the presence of manganese in steel points to a chemical 

 combination of the manganese with the iron. A mere admixture 

 of 2 or 20 per cent, of manganese with iron would not lower the 

 magnetic moment so enormously. Hence it may well be that at 

 certain per-centages a definite chemical union has occurred, and this 

 would doubtless be indicated in those specimens where the mag- 

 netic moment is lowest. 



The study of this question is best followed by an examination 

 of the forged test-bars which were now tried. These bars were 



