Magnetism on a permanent Electric Current. 323 



portional to the mean of the results obtained with the five dif- 

 ferent plates named above. In finding the corresponding 

 number for silver, I have, for obvious reasons, used only the 

 result obtained with the plate of JSTo. 10. The representative 

 number given for tin has been very roughly estimated, and 

 may be one or two hundred per cent, larger or smaller than 

 the true number. All the numbers given must, of course, be 

 taken as at best only rough approximations to the true repre- 

 sentative numbers. 

 We find, then, 



Iron -78 



Silver 8'6 



Gold &8 



Platinum 2*4 



Tin -2(?) 



This arrangement is made on the basis of defining the magni- 

 tude of the action studied as a quantity inversely proportional 



Mx V 



to — = — . If, on the other hand, we were to define the same 



ivr v w 



as inversely proportional to — ==^ — rather, E being the differ- 

 ence of potential of two points a centimetre apart on the lon- 

 gitudinal axis of the metal strip, the representative numbers 

 would be relatively changed. The representative numbers on 

 this new basis may be found by simply dividing each of the 

 representative numbers given above by a quantity proportional 

 to the specific electrical resistance of the metal to which the 

 number is attached. 

 We thus obtain : — 



Iron -80 



Silver 57 



Gold 32 



Platinum' 2*(5 



Tin -15(?) 



It will be observed that the order of arrangement remains 

 unchanged. 



Platinum and tin are carried still further from gold and 

 silver than before ; so that the range of the representative 

 numbers is increased. It is plain, therefore, that by this 

 second arrangement no progress has been made toward finding 

 a constant representative quantity for all the metals. In 

 dealing with the results obtained with different metals, it 

 seems to be of little importance whether we take as our basis 



MxV MxE _ . . , , .., ut 



^ v or — ^7~. When, however, we have to do with dit- 



