310 Mr. R. H. M. Bosanquet on 



Magnetomotive force is a difference of magnetic potential. 

 For any circuit once linked with n spires of an electric cur- 

 rent, the magnetomotive force is 47rC«. 



Magnetic resistance is a linear quantity; for the dimensions 

 of magnetomotive force are 



and of magnetic induction, 



[ir'M^T- 1 ]. 



The idea of magnetizing force as the cause of magnetic 

 induction is abandoned. Magnetizing force is regarded 

 simply as magnetic induction in space or air. Magnetic 

 induction is conceived of as arising directly from the action 

 of magnetomotive force on circuits of magnetic resistance. 



It was shown in my previous paper, that if a permanent 

 magnet of hard steel be divided into short lengths, the sum of 

 the moments is not the same as before, but is greatly reduced. 

 This contradicts the fundamental statement generally received. 

 The chief object of the present paper is the further discussion 

 of the experiment in question. 



It was suggested that, according to the Amperian analogy, 

 permanent magnets may be expected to have permanent mag- 

 netomotive forces in their substance ; and these acting on the 

 magnetic resistance of the circuit would produce magnetic 

 induction, depending partly on the resistance of the steel, and 

 partly on that of the return through space or air. These 

 considerations not only explain the phenomenon in question, 

 but enabled me to foresee it. 



I will shortly recapitulate the experiment. A compound 

 magnet is constructed of eighteen cylindrical pieces, fitted, 

 hardened, and magnetized. centim 



Whole length . . . =28'50 

 Length of each piece . = 1*58 

 Diameter = 1-97 = 2R'. 



These are placed in a cradle hung in a bifilar suspension 

 arranged so that the plane of zero deflection is at right angles 

 to the magnetic meridian. Then, for weeks, there were ob- 

 tained in the mean: — 



Deflection due to 18 pieces joined up . =13°*1 

 „ „ „ separated . = 1°*8 



In the first instance the mean deflection of 1°*05 was obtained 

 with the separated pieces, as stated in my first paper. I have 

 come to the conclusion that this was due to some error in 

 handling the apparatus. When it is at all disturbed the tor- 



