( 407 ) 



it shows us verv precisely the pi'oportiun uf (he resistauces in tlie 

 different magnetic fields, was neither devised nor fit for precise niea- 

 sureraents of the specific resistance. 



First, the distance of the resistance-electrod(;s cannot be accurately 

 determined, and second, it is not certain that the current-lines are 

 entirely parallel with the sides of the plate, a supposition which 

 must be made in the calculation. In order to convince myself that 

 these circumstances did not intiuence the measuring of the increase 

 of resistance I have moreover repeated that measurement with another 

 plate of a very regular shape, electrolytically prepared in the same 

 way. The specific resistance being found to be here 121,000, the 

 percentage increase of resistance was almost the same as in the 

 case of the other plate. 



h. Results of otJwr olserccrs. 



Henderson 



Temp. 18°. 



C,=z 0,2847 



a ==1,798 



Ma''netic tield. 



Foi-ccutafrc iucreasc 



observed 



calculated. 



Difference. 



In order to investigate how far the empirical formula retains its 

 meaning outside the range of the observations which were used in 

 calculating the constants, I substituted the value M =: 38,900, with 

 which Henderson found 233,4o/o ; this gave 245,7°/^ which is in suffi- 

 cient agreement considering the extent of the extrapolation. 



') Wied. Aun. 53 p. 912, 18'.i4. The numbers here uientioiied coueern the measii- 

 remenls with the large spiral of bismuth, which are graphically represented in fig. 4 

 of Table X of that Volume. 



