comets' tails, the corona, and the aurora. 191 



tioii should increase by the same fniction of itself for all parts of the 

 earth. Thus, if A' is the amplitude at a given place in a year of no 

 sun spots, and A its \'alue in a year for which Wolfs nunil)er ex})ress- 

 ing' the relative fre([uency of spots is f, wo ought to lind A = A"^ 

 (l-\-ai). Now, the value of the coefKcient a conies out O.OIHU from 

 whatever part of the wx^rld the observations be taken from which it is 

 calculated. 



]\ietkokitp:s and nebul.e. 



To the man of science this discussion of terrestrial details will 

 pro]>ably be the most convincing part of the evidence adduced by 

 Arrhenius for his theory. But it is time to turn from it and follow 

 with lagging imagination the destinies of those particles, by far the 

 greatest number, which miss tht^ earth and the planets and launch 

 forth into interstellar space. 



Many of them will meet similar streams ejected from othei' suns, 

 and, overcoming the mutual repulsion of their negative charges b^- their 

 mighty velocities, will clash together, like Lucretius's atoms, and unite 

 to form larger masses. But this aggregation must have an end. For 

 if, in the void of space, the}' are unable to get rid of their eh^ctric 

 charges, the potential of the growing mass nuist rapidly increase, since 

 the charge increases as the cube of the radius, being proportional to 

 the total numl)er of particles, while the capacity for holding electricity 

 oidy increases as the radius itself. To put this in popular language, 

 each particle brings to the account the whole charge it can bear on its 

 surface; l>ut in the mass, since electricit}' flies to the surface, oidy the 

 outer parts of those particles which are actually in the surface can be 

 useful in harboring the accunmlating charge, and hence the electric 

 pressure rises. When it becomes intense enough to prevent fresh 

 particles from approaching, accretion will cease. Space will thus be 

 sown with masses of moderate size, formed irregularly, particle l)y 

 particle, in spite of I'epulsive forces. These are the meteorites Avhich 

 blaze for a moment in the upper air, or in rare cases reach the earth 

 to puzzle philosophers with their [)or()us structure. 



Another nudtitude of the particles will at last reach otluu* suns. 

 For if in their wanderings they have united with others till they are 

 beyond the critical size, they will be drawn in, and raise the charge of 

 the bodies they reach, till they in turn discharge thc^ir streams into 

 space. 



In these we see the "greyhounds" of the abyss, engaged in dis- 

 tributing the materials of the universe, forever busied in a cosmic 

 trafHc by whose exchanges the stellar hosts are mad(^ more and more 

 alike in constitution, \vhatev(M- may hav(> l)een theii' difi'erences in the 

 beginning. 



For those myriads which are fated to escapi^ all visible suns, far out 

 in the ""flaming bounds of space" tlui iu>l)uhv lie in wait, spreading 

 spider-like their impalpable webs across inuneasurable breadths of sky. 



