672 BEPORT — 1892. 



an alloy which is not attracted by the magnet, alloys containing 8 to 12 per cent, 

 being only feebly magnetic, and over this proportion they may be said to have 

 practically no influence on the magnet at all. 



Aluminium also possesses a similar property, but in a less marked degree. 

 Ferro-aluminium containing 13 per cent, aluminium is still readily attracted, and 

 it is not until this element reaches 20 per cent, that the effect here alluded to takes 

 place. 



It is therefore an interesting fact that the addition of aluminium to a man- 

 ganese alloy, which of itself would be quite inert, results in an alloy which is 

 readily attracted. 



In one of the alloys exhibited the aluminium is present to the extent of 3'05 

 per cent, only, and although the iron barely reaches 15 per cent, it responds to 

 the influence of the magnet almost as readily as a piece of iron. 



In another alloy which was disintegrated the effect is still more remarkable, as 

 it contains not only manganese but aluminium in sufficient quantity to destroy the 

 influence of the magnet if they were present separately ; yet together they do 

 exactly the reverse, and here, again, although the iron is even less than the above, 

 the magnet attracts it quite easily. 



The alloys which I have drawn attention to were the result of an experiment 

 made to ascertain the possibility of forming a reliable homogeneous alloy of alu- 

 minium with ferro-manganese, and for this purpose 50 lb. of the latter (contain- 

 ing 82 per cent, manganese) and 5-56 lb. of aluminium (containing 99'0 per cent, 

 aluminium) were separately melted in large crucibles, the intention being to make 

 a 10-per-cent. alloy. After they were perfectly fused the ferro-manganese was 

 poured into the aluminium ; after stirring for about half a minute the mixture 

 showed such decided signs of becoming pasty that it was at once poured into an 

 ingot mould. After about two-thirds had been poured the remainder suddenly 

 solidified, and was roughly knocked out of the crucible. 



The alloys presented no apparent dissimilarity, and it was not thought worth 

 while to examine them until after keeping for about three months the portion 

 which had solidified first commenced to fall into pieces — in the same way that 

 high-percentage ferro-manganese of 85 per cent, is known to do — and this action 

 has gone on until it has almost completely disintegrated, and is now in the condition 

 of the specimen shown. 



The analyses of the two portions showed a remarkable difference in composi- 

 tion. The disintegrated portion contains — 



Iron 10-80 



Manganese 5486 



Carbon 2-32 



Aluminium .......... 25-34 



Silicon 0-79 



Sulphur traces 



Phosphorus 0-107 



Copper 0-075 



94-292 



This analysis was repeated with practically identical results. The deficiency is 

 no doubt due to slight oxidation having taken place owing to the finely divided con- 

 dition of the alloy: it has a specific gravity of 3'61. The examination of the 

 portion which was poured off showed it to laave a specific gravity of 6-12, and 

 that it contained — 



Iron 14-80 



Manganese 75-40 



Carbon 5-55 



Aluminium .......... 3-05 



Silicon -886 



Sulphur trace 



Phosphorus 0184 



Copper -07. 'i 



99-945 



