( 403 ) 



SS, = r„ % + V,, %, + r„ ^3I„ 

 which we shall condense into the formula 



i» = (v) 5i. 



According to this notation we may put Q=z(i)')^, or, as is more 

 convenient for our purpose, 



^ = {p)^ (3) 



the sj-mbol (p) containing a certain number of coefïicients p which 

 are determined by the properties of the body considered. As a rule, 

 these coefficients are complex quantities, whose values depend on 

 the frequency n. 



As to the relation between ^ and S^, we shall put 



^ = (/^) •C^ 



or 



'C) = (?)53 (4) 



We have further to introduce an electromotive force wliicli will 

 be represented by a vector ^'e, or by the real part of a complex 

 vector ^i'e- Tiie meaning of tiiis is simply that the current 6 is sup- 

 posed to depend on the vector (£' + ^'e in tlie same way in which it 

 depends on ^ alone in ordinary cases, so that 



C + (re = (/>)e (5) 



Similarly, we may assume a magnetomoti\e force .^\, replacing 

 (4) by ' 



^^? + 'C\ = (7) ^ (6) 



This new A'ector -Oe however, does not correspond to any really 

 existing quantity; it is only introduced for the purpose of simplifying 

 the demonstration of a certain theorem we shall have to use. 



As to the coefticients we have taken tcgetiier in the symbols (p) 

 and (q), we shall suppose them to be connected witii each other in 

 the way expressed by 



and 



Ql2—92V '7^3 ='732' 731='?13 (8) 



The only case excluded by this assumption is that of a body 

 placed in a magnetic iield. 



For isotropic l^odies we may write, instead of (5) and (6), 



(ï + ^-,=:2>6, (9) 



.f) + .r->, = ^ >JS (10) 



with only one complex coefficient j^ i^nd one coefficient q. 



