1883.] 



On a Magnetic Balance. 



171 



wires, kindly furnished me expressly for these experiments by 

 Messrs. Frederick Smith and Co., of Halifax : — 



Table II. 



Marked. 



a 



F 



T 



S 



H 



Y' 



Y 



Z 



Best Swedish charcoal iron, 1st variety. 



2nd „ . 

 „: „ 3rd „ . 



Swedish, Siemens-Martin, iron 



Puddled iron, best best 



Bessemer, soft steel 



Bessemer, hard steel 



Crucible fine cast steel 



Magnetic capacity. 



Bright hard 

 drawn. 



230 

 236 

 275 

 165 

 212 

 150 

 115 

 50 



Annealed. 



525 

 510 

 503 

 430 

 340 

 291 

 172 

 84 



The above series contains representative irons and steel of all 

 classes, all other varieties yet tried stand between cast steel and Swedish 

 iron, generally classed as hard cast steel, hard steel, mild steel, hard 

 puddled iron, soft iron, Swedish charcoal iron. 



From the above table it will be seen that every wire rises greatly in 

 value by annealing, and that we could not estimate the true magnetic 

 capacity of any iron or steel unless special attention was given that all 

 should be annealed to their maximum. 



The influence of tempering upon the magnetic retentivity or 

 molecular rigidity has been shown in every piece of iron or steel 

 examined, the molecular rigidity of tempered cast steel being pro- 

 portional to its species of temper as shown in Table III. 



Table III. 

 Tempering. 



Magnetic capacity. 



Crucible fine east steel, tempered. 



Bright yellow heat cooled in cold water 28 



Yellow red „ „ 32 



Bright yellow tempered in cold water let down to 



straw colour ....... 33 



Bright yellow tempered in cold water let down to blue 43 



Bright yellow tempered in oil - 51 



Bright yellow tempered in water let down to white . . 58 



Red heat tempered in water 66 



Red heat tempered in oil 72 



Crucible cast steel annealed 84 



Swedish charcoal iron annealed 525 



