358 Mr. H. A. Rowland on Magnetic Distribution. 



Table XIT. 

 Stub's Steel. 





Electromagnet. 



Permanent magnet. 



Magnetism 



Magnetism 



Magnetism 



Magnetism 



Same as third, 



w. 



same as 



opposite to 



same as 



opposite to 



after three or 





original. 



original. 



original. 



original. 



four days. 



Qe. 



4tt\. 



Qe. 



4tt\. 



Qe. 



4ttX. 



Qe. 



47rX. 



Qe. 



4ttX. 







i 



2 

 1 



1* 



2 

 3 

 4 

 6 



23-3 

 11-5 



42-5 



230 



159 



7-7 



290 

 15-4 



1 14-4 



137 



4-8 



4-6 



128 



12-2 



8-2 

 6-1 



16-4 

 122 



5-9 

 4-3 



11-8 

 8-6 



| 8-2 



8-2 



40 



40 



73 



73 



74 



7.4 



5-5 



5-5 



5-3 



5-3 



2-9 



2-9 



4-8 



4-8 



3-6 



36 



2-7 



2-5 



30 



30 



16 



1-6 



2-9 



2-9 



17 



•8 



10 



•5 



22 



11 



•9 



•4 



20 



10 



The observations in Tables- XL and XII. can be compared 

 together, the quantities being expressed in the same unknown 

 arbitrary unit. It is to be noted that the bars in Tables XI. and 

 XII. were subjected to the same magnetizing force. 



First of all, from these Tables and figures (p. 359) we notice the 

 change in distribution due to the quality of the substance; thus 

 in fig. 5 we see that the curves for steel are much more steep than 

 that of iron, and would thus give greater values to r in the for- 

 mula — a result to be expected. We also observe in both figures 

 the great change in distribution due to the direction of magneti- 

 zation. In the case of the electromagnet this amounts to little 

 more than a change in scale ; but in the permanent magnet there 

 is a real change of form in the curve. It seems probable that 

 this change of form would be done away with by using a suffi- 

 cient magnetizing power or magnetizing by application of per- 

 manent magnets ; for it is probable that the fall in the curve 

 E is due to the magnetizing force having been sufficient to change 

 the polarity completely at the centre, but only partially at the 

 ends. 



On comparing the distribution on electromagnets with that 

 on permanent magnets, we perceive that the curve is steeper 

 toward the end in electromagnets than in permanent magnets. 

 At first I thought it might be due to the direct action of the 

 helix, but on trial found that the latter was almost inappreci- 

 able. I do not at present know the explanation of it. 



As before mentioned, Coulomb has made many experiments 

 on the distribution of magnetism on permanent magnets ; and 

 so I shall only consider this subject briefly. I have already 

 given one or two results in Table XII. 



