36 EVOLUTION 



at side by side with its own final historical outcome. In 

 Mr. Spencer's perspicuous phrase, evolution in this aspect 

 is a change from the homogeneous to the heterogeneous, 

 from the incoherent to the coherent, and from the indefinite 

 to the definite condition. Difficult words at first to appre- 

 hend, no doubt, and therefore to many people, as to Mr. 

 Matthew Arnold, very repellent, but full of meaning, lucidity, 

 and suggestiveness, if only we once take the trouble fairly 

 and squarely to understand them. 



Every sun and every star thus formed is for ever 

 gathering in the hem of its outer robe upon itself, for ever 

 radiating off its light and heat into surrounding space, and 

 for ever growing denser and colder as it sets slowly towards 

 its centre of gravity. Our own sun and solar system may 

 be taken as good typical working examples of how the 

 stars thus constantly shrink into smaller and ever smaller 

 dimensions around their own fixed centre. Naturally, we 

 know more about our own solar system than about any 

 other in our own universe, and it also possesses for us a 

 greater practical and personal interest than any outside 

 portion of the galaxy. Nobody can pretend to be profoundly 

 immersed in the internal affairs of Sirius or of Alpha 

 Centauri. A fiery revolution in the belt of Orion would 

 affect us less than a passing finger-ache in a certain single 

 terrestrial baby of our own household. Therefore I shall 

 not apologise in any way for leaving the remainder of the 

 sidereal universe to its unknown fate, and concentrating 

 my attention mainly on the affairs of that solitary little, 

 out-of-the-way, second-rate system, whereof we form an in- 

 appreciable portion. The matter which now composes the 

 sun and its attendant bodies (the satellites included) was 

 once spread out, according to Laplace, to at least the 

 furthest orbit of the outermost planet that is to say, so 

 far as our present knowledge goes, the planet Neptune. Of 



