﻿560 iDr. G. Bakker on the 



Putting \ = - , \ being a length, we have thus for the 

 potential energy per unit of volume : 



-^/( R2+ 5) ^ 



That is, changing the sign, the work to be done in conveying 

 the parts of the unit of volume to an infinite distance from 

 each other, or, which is the same thing, beyond the sphere of 

 sensible activity. 



§ 3. Tensions in the medium. — Let us embrace within a 

 surface one part of the homogenic agent we have under 

 consideration ; this would be system L, the rest we call 

 system II. The force resolved parallel to the axis of no 

 of the forces exercised by system II. on system I. is 

 expressed by 



or, substituting for p the value derived from (3), 



- 47T/X! = f A 2 V |^ dx dy dz - rf f V |^ dx dij dz. 



/avy /avy /avy 



Putting 



(! . 



we shall find &c, 



an integral which would immediately transform into a surface- 

 integral relative to the surface which limits system I. : — 



x i — J (fa** + m Pyz + n P*x) ds - 



In the same manner one would obtain the values of Y x 

 and Z]. 



In proceeding according to Maxwell in his electrical agent, 

 one would deduce from the values of X 1? Y l5 and Z 1? the 

 existence of a cohesion Si in the direction of the lines of 

 force and a, tension S 2 in the perpendicular direction, these 

 cohesions being represented by 



S '=-4( R2 -?) a " d 8 > = «fe( R2+ 5} 



(5) 



