Eqiupotential Lines of an Electric Current. 139 



In a thin disk magnetized longitudinally, i. e. in a direction 

 normal to the faces, the law is £= EL. The effective portion of 

 cross N~o. 5 is fairly well represented by such a disk, and we 

 shall assume that with this cross B was nearly equal to H. 



In case of a disk magnetized transversely, i. e. parallel to its 

 faces, the diameter being to the length as 6 to 1, 



_Z?= approximately 8 H. 



As the thickness of cross No. 8 was about 3 mm and as the width 

 of the main part was in general about 05 mm , it might be 

 thought that this cross presenfed a case similar to this latter 

 disk, but it must be remembered that the effective portion in- 

 cluded the bases of the arms. It is likely, too, that both the 

 main part and the arms were somewhat more than OS 111111 wide 

 at the junction. The case lies, probably, between that of the 

 disk magnetized transversely and that of the sphere, but nearer 

 that of the sphere. It seems not unlikely then, that in a field 

 of moderate strength, such as would not bring either cross near 

 to the condition of " saturation," No 8 might become four or 

 five times as strongly magnetized as No. 5. It will be remem- 

 bered that in the experiments of Jan. 7th, with a field of 

 moderate intensity the R. P. of No. 8 was about 4^ times as 

 great as that of No. 5. 



The primary object. of these experiments was to obtain new 

 evidence bearing upon the question whether the transverse 

 effect studied is due to a distortion of the cross as a whole 

 under the combined action of the ordinary " pondero-motive 

 force," as Mr. Eidwell and, doubtless, others have supposed, or 

 to some internal interaction, which for want of a better term 

 may be called molecular, of the magnetic and electric states of 

 the conductor. The results obtained lend no support to the 

 former of these two hypotheses, but they are in complete accord 

 with the latter, which must, I think, be regarded as established. 



Wishing to study still further the connection between the 

 internal magnetic condition of iron and the transverse effect in 

 it, I have made recently a series of experiments comparing the 

 behavior of the two broad crosses No's. 5 and 7. Instead of 

 depending here upon a calculation of the ratio of the magnetic 

 inductions in the two, I have tried to measure this roughly by 

 a method which I will describe somewhat fully, as I shall 

 probably make use of it in future experiments. A loop 

 of thin well-covered -wire (the diameter to outside of covering 

 being about 0*25 mm ) was placed flat upon each of these crosses 

 between the arms, was pressed well down and secured in place 

 and shape with the usual cement of beeswax and rosin. Each 

 of these loops was somewhat elliptical in shape, that on No. 5 

 being about 7'4 mm wide and 124 mm long, and the one on No. 7 



