382 THE WORLD MACHINE 



of the spacing of the luminous suns. These probable collisions, 

 combined with the evident number of binary systems, tend to 

 confirm the conclusion we have reached upon other grounds, 

 as to the enormous number of dark bodies. More than thirty 

 years ago, and before the variety of evidence now at hand had 

 been accumulated, Professor Johnstone Stoney, from a pro- 

 found study of stellar phenomena, was led to say : 



"If what I here venture as a surmise with respect to the 

 cause of stellar heat and the origin of double stars, is what 

 really takes place, we must conclude the sky to be peopled 

 with countless hosts of dark bodies, so enormous that those 

 which have met with such collisions as to render them now 

 visibly incandescent must be comparatively few indeed." I 



The astronomy of the invisible, it will be perceived, is as 

 yet in its infancy. There is already sufficient to indicate that 

 its field is immense that is to say, that the number of dark 

 bodies probably far transcends the number of those which the 

 telescope brings in view. In a sense this is yet a surmise. It 

 is obvious that until the matter can be cleared up our know- 

 ledge of the cosmos can at best be incomplete, our conjectures 

 as to its form and structure but provisional. 



It is only very recently that this fact has become clear. In 

 ignorance of it, the astronomers did not hesitate to build up 

 vast systems which had little larger foundation perhaps than 

 their own imaginations. It will perhaps be of interest, never- 

 theless, to pass them in review, and endeavour to sift out any 

 elements of truth they may contain. Possibly from the wreck 

 of them we may gather some ideas. 



1 Proc. Royal Society, 1861-69. 



