86 LIGHT SCIENCE FOR LEISURE HOURS. 



he supposed, comparatively young ; they showed no 

 signs of systematic aggregation or of central condensa- 

 tion. In some nebulae he traced the approach towards 

 the formation of subordinate centres of attraction ; 

 while in others, again, a single centre began to be 

 noticeable. He showed the various steps by which 

 aggregation of the former kind might be supposed to 

 result in the formation of star-clusters, and condensa- 

 tion of the latter kind into the formation of conspicuous 

 single stars. 



But it was felt that the strongest part of Herschel's 

 case lay in his reference to the great nebula of Orion. 

 He pointed out that amongst all the nebulae which 

 might be reasonably assumed to be star-systems, a cer- 

 tain proportionality had always been found to exist 

 between the telescope which first detected a nebula and 

 that which effected its resolution into stars. And this 

 was what might be expected to happen with star- 

 systems lying beyond our galactic system. But how 

 different is this from what was seen in the case of the 

 Orion nebula. Here is an object so brilliant as to be 

 visible to the naked eye, and which is found on exami- 

 nation to cover a large region of the heavens. And 

 yet the most powerful telescopes had failed to show the 

 slightest symptom of resolution. Were we to believe 

 that we saw here a system of suns so far off that no 

 telescope could exhibit the separate existence of the 

 component luminaries, and therefore (considering merely 

 the observed extent of the nebula, which is undoubtedly 

 but a faint indication of its real dimensions) so incon- 



