( 58 ) 
and attending to (5), we see that 
00: 0 Dy OM, 1 d&, 
ne Na + —— a 
dy dz A ewe trp 
Now, let a new vector D be defined by the equation 
D—=—M+ 5 
D= = . . . ° . . . 2 
Any?’ Se 
then 
0H: dD, 0D. df: dz 0D, 
— —- — =47—  , —— — - =dn —, 
Oy z ot dz Ox Ot 
0fy OP, ORDE 
DE ae == dr ie (| 
Since € is the electric force, €/4 av? will be the dielectric dis- 
placement in the aether; D will therefore be the total dielectric dis- 
placement and D the displacement-current. Thus the equations (1’) 
are seen to contain the well known relation between the magnetic 
force and the electric current. 
In (1), (2), (3') and (4') we have got the complete system of 
eauations of motion. We might have obtained them also by starting 
from the relation between € and M, which I have assumed in my 
„Versuch einer Theorie der electrischen und optischen Erscheinungen 
in bewegten Körpern”; it would only have been necessary to add 
the terms which arise from a resistance and from the action of a 
magnetic field. The above method is less simple, but it goes farther 
in explaining the mechanism of the phenomena. 
S 5. Now, it is easily seen that the equations of the electro- 
magnetic theory are identical with those of Vorer, if in these latter 
only one vector P is assumed. 
Indeed, if, in the formulae of Vorer, we replace 
Ou ov dw os 6 
Be Bek vy ’ = Nn, ef OF Vv; WW. =) El 4 
by 
De pe ty Pe Be ey 
Amv?’ Anv2' 4nv2’ y2’ vy" yy’ 
