( Bl4 ) 



ail eicel roil relains ils eluirgv, and 2"^^ llial the eoiidition (I) is eoii- 

 tiniially fulfilled. 



§ 5. Lel lis Ijegiii hv eoiisidei-iiiii' (f i\,. This is liie variation in 

 a fixed |>(tiiil of spaee. Therefore, if (^Uv) is tlie ^'al•iation for a 

 definite |)oiiil of an eleelron, we shall have 



dr^i div d'Ox 



O.r Of/ 0: 



As to {(hj), it is easily shown to have the value 



at 



(la, 

 Ü we understand 1)\- ~- the rate at which ci, chanoes for a delinite 



(/t 



point of an eleetron. C'oni|)ariiig' this to ^ or q.,, the x'clocity of 



change in a fixed point of sjiaee, we get 



öji öiir öctr 



{dv.) =- q.v + v.r V" + i)// -y- + I- T^ . 



0./- 0// OC 



These equations, coiuhined with (7), lead us to 



(fla- z= Ö (^,. -|- ^ iv) = ^^ ^./ + (> f ^ i\, + i\i d o = 

 d.^f 0.^,. 0.1, 



O.r 0>/ Oz 



~ ^ ^' d.v ~~ ^ '^'^ 0^' — ^ ^1^ ()- - ^^•' '^''" ^? ^)' 



ÖOx Öiv ölV 



•7/ 



<ir, if we add to die second ineiuher \\\c lirsl ineniher of (Ilj, niiilii- 

 plied l»y q.,> after s(»iiie further Iraiisfornialion, 



Ö c)q, ó^^ öq,- 



our Öiv,, ÖO, 



" ^ '"^ '■ ö7 ~ ^ '"'•^ d7 "~ ^ '^' "ö^ + '''■'■ '^''" ^^' ^'^ ~ 



Ö d Ü 



= ö7 (^ ^' + ^ ''' '^ ^ d7 '-^ ^''•' *■'■' ~ '^'' ^^'-^^ ~ 0^ ' '' ^'^' ^' ~ '^■' ^''^'' 



Here we may remark that the two last terms taken together repre- 

 sent the first component of the "rotation" of the A'ector whose com- 

 ponents are 



C (q.V l^r — qr ih/)' Q (qr l\, — C\,- l\-)- Q {<Vr i\,, — C\>/ ih). 



and that this vector is precisely the vector-product, multiplied by 

 Q, of q and i\ After having calculated öl,f and di- in the same Avay 

 as öii-, we luixy combine the results in tiie formula 



