70 
Two nebular spheres, each with a mass of 7.10* gr. and a radius 
of 200 Neptune orbit radii have centres which are at a distance of 
1000 Neptune orbit radii from each other. The density, like the 
intensity of radiation, is again considered constant inside the nebula. 
The quantity P, which occurs in the formulae (5) and (6), may 
be written: 
—2 Be 
P= au Os R, R 5 = ; 5 5, sd A (7) 
in which «, 9, and &, have the same value as in the preceding §, 
in which R,/R is, however, + 300 times smaller. Then the value 
of P becomes so small that we may write instead of (5): 
‘4 RS 
Ae 
== A 
(8) 
Assuming that of this quantity of radiation, which one nebula 
sends to another, the n'' part is absorbed by the latter sphere, this 
experiences a pressure of radiation which may be written after 
some reduction: 
MM, S — 8R 
ae! As "n’ 4fco, BR pag aon ae AE 
When numerical values are introduced, we get: 
MM, As 
ese leer 
1 
Even on the assumption that only 100.000.000 of the received 
radiation is absorbed, the value of S need not be more than 
0,3.10-7 to render the effect of the pressure radiation as great as 
that of gravitation. In the case of black radiation, a temperature 
of some tens of degrees above the absolute zero would already 
suffice to bring it about. The real temperature will on an average 
certainly be higher, besides in this case considerable luminiscence 
should also be taken into account, so that we come to the conclusion: 
There is every reason to expect that in nebulae with some conden- 
sation nuclei the gravitation of the different parts on each other has 
greatly diminished, if it is not quite exceeded by the mutual pressure 
of radiation. 
For the rest it should be pointed out that this diminution of 
gravitation only refers to the internal gravity. Towards the outside 
the ordinary Newtonian attraction remains valid. 
