14 THE LESSON OF EVOLUTION 



Way ; no Orion nor Southern Cross ; no Pleiades nor 

 Dog-star. All these, and many others, have been 

 added since : not all together, but one after the other, 

 through the long ages during which the sun was 

 undergoing development. Judging by the relative 

 ages of the stars, it seems probable that the process of 

 concentration of the original cosmic dust commenced 

 near the Solar System and spread outwards to the 

 Milky- Way. But, however this may be, the process 

 is not yet over. Many nebulfe have not yet con- 

 densed into stars. Swarms of meteorites still traverse 

 space ; and even in the neighbourhood of the Solar 

 System they are so abundant, that the Earth alone is 

 estimated to collect more than twenty millions each day. 



However, slow as the process of condensation is, it 

 is not endless. In time all the meteoritic dust will be 

 collected into stars or planets ; and in time the law of 

 dissipation of energy will bring all these bodies to a 

 uniform temperature. So at last the movements due 

 to the original unequal distribution of matter will 

 cease, and the life of the Universe will come to an end. 

 We know of no process of rejuvenescence, by means of 

 which dissipation of energy and the force of gravita- 

 tion might be counteracted. Several attempts have 

 been made to refute the theory of the dissipation of 

 energy, but all have failed. 1 



The ether, which pervades space, is the only part of 



1 The last champion in the field is Professor A. W. Bickerton, who 

 thinks that he has found a way in which this dismal conclusion, as he 

 considers it, may be averted. But he is not very sure about it, and 

 has to assume : first, that space contains now, and always will con- 

 tain, a large quantity of cosmic dust scattered through it with some 

 approach to uniformity ; and, secondly, that the Universe consists of 

 an infinite number of what he calls "cosmic systems," travelling 



