( 4.12 ) 

 iintl ilii' i'mictloii f.)y itscll' will sntisfy llic i-imilition 



^-^ + ^-^ + ^-^ — — 471 I - (y„ — — P - ,>. 



Cnnipariiif;- this with (2), wo. wo Hint in onnospondinr;; points 



and onnsoqnont]} 



Ts'^ — e,.r , 5V = ^' »/ ' ?'- = ^'>^- 



Tn Yirtuc of what, has hoon roniaiked at the end of § 4, the 

 oompononts of tho ehsotrio loieo in tho syst(>m 'S' will thoioforo be 



l^iiallel to OX we have the same electric foroo in -S' and .S',,, hut; 

 in a direction perpendicular to OX the electric force in S will be 



— times the electric force in 'S'^. 



By means of this result every electrostatic problem for a moving 

 system may be reduced to a similar problem for a system at rest; 

 only the dimensions in the direction of translation must be slightly 

 different in the two systems. If, e.g., we wish to determine in 

 what way innumerable ions will distribute themselves over a moving 

 conductor C', we have to solve the same problem for a conductor 

 Cq, having no translation. It is easy to show that if the dimensions 

 of Co and C differ from each other in the way tliat has been indi- 

 cated, the electric force in one case will be perpendicular to the 

 surface of C^ as soon as, in the other case, the force ^^ is normal 

 to the surface of Cg. 



Since 



exceeds unity only by a (juantity of tlio second order — if we call 

 -r of the first order — the influence of tho earth's yearly motion 

 on oh'clrostatic phenomena will likewise be of the second order. 



