k nae 
Ek OE AO nat Se ee 
a 
where C is an arbitrary integration constant. For the Lorentz elec- 
m 
tron we have an m = —-. If we postulate that the corresponding 
equation for the energy will also hold good, namely / + U+ E= 
1 
ret + U, + Lo), then we must put C= 0 and we find again 
for ZE the value calculated by Potncaré and ABRAHAM. 
Now it appears a posteriori that 
Oi g T—U--E)=6 
i ot —U--E)=6 
From this follows that the two corrections which we mentioned 
above need not be applied to © in order to find ©; The two 
corrections appear to cancel each other. This result is remarkable. It 
proves that the energy inside the electron is stationary in space. At 
the frontside Poynting’s vector is directed towards the electron. 
Hence when the energy reaches the frontside of the electron it 
is suddenly stopped in its motion and it remains at rest inside the 
electron till it is reached by the backside of the electron. Then it 
is- again put into motion as radiating energy, but now the motion 
is directed away from the electron. 
I will remind that the usual way of calculating the radius of the 
electron depends on the supposition that ©,,,—= ©. For the applica- 
bility therefore of this calculation it is decisive whether or no the 
suppositions assumed above are correct. 
dst. that the supplementary energy ZE must be introduced in the 
function of LAGRANGE as potential energy, in agreement with the 
assumptions of Poincaré and of ABRAHAM. 
: 1 
2nd, that the mass of the electron is equal to its energy X-. 
c 
Chemistry. — “Amygdalin as nutriment for Aspergillus niger.” IL. 
By Dr. H. I. Waterman. (Communicated by Prof. Dr. J. 
BOESEKEN. ) 
(Communicated in the meeting of February 24, 1917). 
In an earlier communication *) I have shown that amygdalin is 
a better nutriment for Aspergillus niger than glucose, at least with 
regard to the weight of mycelium obtained. 
1) These Proceedings January 26, 1917 p. 922. 
