238 



MR J. C. BEATTIE ON THE 



The equations for such a body would be 



X = r n u + r 12 v + r 13 w 

 Y = r 12 w + r 22 v + r 23 w 



'13" 



'23" 



'33" 



If to this we add the fact that a magnetic field gives rise to a rotatory coefficient as 

 well, which is an odd function of the magnetisation, we have the most general equations 



X = r n u + r 12 v + r 13 w + T 3 v - T 2 w> 

 Y = r 12 u + r 22 v + r 23 to + TjW - T 3 ?< 

 Z = r 13 u + r 23 v + r 33 w + T 2 w - Tj« 



where x, y, z are the components of the electromotive force parallel the three axes ; 

 u, v, iv the components of the current ; p n , r 22 , r 3S the direct resistances ; r 12 , r 13 , r 23 the 

 transverse resistances ; T u T 2 , T 3 the rotatory resistances. 



The second effect was not observed in all the plates. Its presence was observed by 

 the gradual decline of the galvanometer deflexion of the transverse current, which lasted 

 for about a minute, when a steady state was usually reached. It was measured in the 

 following manner : — After the steady transverse reading had been taken, the electro- 

 magnet was kept on, the primary current was broken, and the galvanometer immediately 

 inserted. The reading thus obtained was usually small and died away gradually. In 

 every instance it was oppositely directed to the transverse current. 



Plate I. 



Length, 



Breadth, 



Thickness, 



5-45 



2-96 

 0-1305 



cm. 



Field, 

 Effect, 



9-6 

 0-0069 



36-8 

 0-0319 



58-0 

 00437 



119-0 

 0-0429 



131-5 



0-0381 



141 



0-0371 



The numbers given under " effect " are here, as before the galvanometer reading, 

 divided by the primary current. 



The same plate was previously used, its thickness then being 0'19416 cm. 



Field, . 



24-0 



52-2 



98-0 



114-2 



131-0 





, Effect, . 



0-0213 



0-0288 



00334 



0-0343 



0-03133 









Plate ] 



[I. 







] 



] 

 1 



jength, 



3readth, 



"hickness, 



• 



* * 



6-26 cm. 

 2-945 „ 

 0-1497 „ 



, 





Field, . 



36-0 



61-0 



120-0 



137-0 



146'0 





Effect, . 



0-01746 



0-0343 



0-0718 



0-0806 



0-084 





