Magnetization of Soft Iron Bars. 455 



the data we have in the curves figs. 1 to 5. To do this we have 

 to reduce the bars to some common length and find their 

 several diameters which will make their shapes similar to the 

 original ones. Taking their common length to be 1 cm., 

 and finding the diameters and volumes which each of the 

 bars would come to have, we obtain from the Table given in 

 page 452: — 



Reference number. 



Reduced diameters. 



Reduced volumes. 



I. 



•0253 cm. 



•00051 cub. cm. 



II. 



0312 „ 



•00077 „ „ 



III. 



•0380 „ 



•00114 „ „ 



IV. 



•0507 „ 



•00203 „ „ 



V. 



•0765 „ 



•00457 „ „ 



To find, now, the induced magnetic moment due to any- 

 field in any of the reduced bars, we have to take the mean 

 intensity of magnetization corresponding to that field from 

 the particular curve which belongs to the original bar; and 

 multiply that intensity by the reduced volume. The dia- 

 gram (fig. 14) shows the increase of magnetic moment 

 due to the increase of the section of soft iron bars deduced 

 in this way. On the top of the diagram numbers indicat- 

 ing the ratio (diameter/length) are placed for convenience 

 of reference. The moment here being given in O.G.S. 

 units for bars of 1 centim. long, we can find the moment 

 of induced magnetism due to any field for a soft iron bar of 

 any given dimensions, supposing the magnetization to be 

 independent of the absolute size of the bar. For this purpose 

 we have to take the moment corresponding to the particular 

 ratio (diameter/length) of the given bar and the particular 

 field required, and multiply that moment by the cube of the 

 length. That is to say, within the limits to which the experi- 

 ments extend. 



The curves are similar in character to those obtained with 

 a bundle of wires, only they are not so decidedly asymptotic 

 as the latter. We cannot, however, draw a definite conclusion 

 as to the real difference between the two cases, on account of 

 the difference of the specimens of the wires employed. From 

 both sets of these experiments we see that, after the diameter 



