( 565 ) 
Now, it is clear that, by our assumptions, the flow of energy 
must be symmetrical all around Q; hence, if an amount Z of energy 
traverses, in the outward direction, a spherical surface described 
around Q as centre with radius 7, we shall have 
E 
foe a a 
4 nr” 
and the force on P will be 
K— n eb E 
An V272 
It will have the direction of QP prolonged. 
In the space surrounding Q the state of the aether will be sta- 
tionary; hence, two spherical surfaces enclosing this particle must 
be traversed by equal quantities of energy. The quantity / will be 
independent of 7, and the force & inversely proportional to the 
square of the distance. 
If the vibrations of Q were opposed by no other resistance but 
that which results from radiation, the total amount of electro-mag- 
netic energy enclosed by a surface surrounding Q would remain 
constant; £ and & would then both be 0. If, on the contrary, in 
addition to the just mentioned resistance, there were a resistance of 
a different kind, the vibrations of @ would be accompanied by a 
continual loss of electro-magnetic energy; less energy would leave 
the space within one of the spherical surfaces than would enter 
that space. ZL would be negative, and, since b is positive, there 
would be attraction. It would be independent of the signs of the 
charges of P and Q. 
The circumstance however, that this attraction could only exist, 
if in some way or other electromagnetic energy were continually 
disappearing, is so serious a difficulty, that what has been said cannot 
be considered as furnishing an explanation of gravitation. Nor is 
this the only objection that can be raised. If the mechanism of 
gravitation consisted in vibrations which eross the aether with the 
velocity of light, the attraction ought to be modified by the motion 
of the celestial bodies to a much larger extent than astronomical 
observations make it possible to admit. 
§ 5. Though the states of the aether, the existence and the laws 
of which have been deduced from electromagnetic phenomena, are 
found insufficient to account for universal attraction, yet one may 
try to establish a theory which is not wholly different from that of 
