Very — On a Possible Limit to Gravitation. 43 



central forces different from gravity are at work among 

 the nebnlae. On the contrary, since gravitation is found 

 by observation to govern the motions of the stars, and 

 the nebulae pass by insensible gradations into stellar 

 systems, as is conclusively shown in this volume, it nec- 

 essarily follows that the central forces operating in the 

 nebulae can be nothing else than universal gravitation; 

 which is a last and sufficient proof that the observed 

 figures of the nebulae are chance spirals, and therefore 

 depart from any kind of geometrical regularity." 



If it had simply been said that it is not to be supposed 

 that gravitation is not at work in the nebulae, because it 

 is obviously at work in their stellar components, no 

 objection could have been made to such a statement ; but 

 when the universally present and peculiar nebular fea- 

 tures are ignored and attributed to " chance, " and no 

 real attempt is made to explain them, there is urgent 

 need of a different treatment of the data. 



It seems to me that Sutherland has supplied the essen- 

 tials of a correct version. The indications are over- 

 whelming that, while gravitation may not be absent, a 

 different force is in control in these large-scale opera- 

 tions. This force acts according to the inverse cube of 

 the distance and is probably magnetic. The law of the 

 logarithmic spiral covers the case well enough. It is not 

 necessary to pin one's faith to some one definite system 

 of logarithms. Sutherland's method picks out that 

 variety of logarithmic spiral which most nearly fits a 

 given case. .There are minor deviations which, like the 

 irregularities in comet's tails, point to secondary causes, 

 some of which may be of considerable magnitude ; but 

 these do not disprove the continued action of the major 

 force. Thus, for the comet's tail, this force is the pres- 

 sure of sunlight; and for the spiral nebula it is the 

 magnetic currents of the aura, both of them forces which 

 at first sight seem impalpable, but forces whose power 

 comes from the enormous spaces through which they act. 



If it be asked how the currents of the aura can control 

 the motions of the stellar systems, I would answer that 

 the gravitational field is in the aura and that, while the 

 energy which is matter is concentrated in material par- 

 ticles, this energy has. its complementary reaction which 

 is diffused through an entire sphere of aura. It is, in 

 fact, the interaction of these interpenetrating gravita- 



