1908] on the Ether of Space. 69 



Appendix I. On Gravity and Etherial Tension. 



Stating the law of gravitation as F = y — ^, the meaning here 

 adopted for etherial tension at the surface of the Earth is 



SO that the ordinary intensity of gravity is 



6?T yE 4 ^ 



Accordingly, near the surface of a planet the tension is Tq = g R, or 

 for different planets is proportional to p R^. 



The velocity of free fall from infinity to such a planet is V(2 Tq) ; 

 the velocity of free fall from circumference to centre, assuming 

 uniform distribution of density, is V (Tq) ; and from infinity to centre 

 it is V(3 Tp). 



Expanding all this into words : — 



The etherial tension near the earth's surface, required to explain 

 gravity by its rate of variation, is of the order 6 x 10^^ cg.s. units. 

 The tension near the sun is 2500 times as great. With different 

 spheres in general, it is proportional to the density and to the super- 

 ficial area. Hence, near a bullet one inch in diameter, it is of the 

 order 10- ^ ; and near an atom or electron about 10" ^'. 



In order to set up a tension equal to the critical, or presumably 

 disruptive, stress in the ether [10^^ c.g.s.], a globe of the density of 

 the earth would have to have a radius of eight light years. In order 

 to generate a velocity of free fall under gravity equal to the velocity 

 of light, a globe of the earth's density would have to be equal in 

 radius to the distance of the earth from the sun, or say 26,000 times 

 the earth's radius. If the density were less, the superficial area 

 would have to be increased in proportion, so as to keep p W constant. 



The whole visible universe within a parallax of yoW second of 

 arc, estimated by Lord Kelvin as the equivalent of 10^ suns, would 

 be quite incompetent to raise etherial tension to the critical point 

 10^^ c.g.s. unless it were concentrated to an absurd degree ; but it 

 could generate the velocity of light with a density comparable to that 

 of water. 



If the average density of the above visible universe (which may 

 be taken as 1*6 X lO-^^ grammes per c.c.) continued without limit, 

 a disruptive tension of the ether would be reached when the radius 

 was comparable to 10^^ light years : and the velocity of light would 



