56 ON SOME ASPECTS OF THE 



one mode changing to another without any energy ceasing 

 or being lost in the transformation. 



Such an imaginative flight is far beyond all sense 

 experience. To the thought of a scientific man the 

 universe, with all its suns and worlds, is throughout one 

 seething welter of modes of motion, playing in space, 

 playing in the ether, playing in all existing matter, playing 

 in all living things, playing, therefore, in ourselves. Now 

 locked together in more intimate embrace, potential 

 energy, now unlocked and streaming as kinetic energy 

 through space, continually alternating between these two 

 settings, this eternal motion never ceases, is never 

 dissipated, and is never recreated ; it simply exists. 

 The conception thrills the imagination like a poem. It 

 is probably for this reason that it is always associated 

 in my mind with the beautiful sonnet which Wordsworth 

 composed as he walked the beach at Calais : 



It is a beauteous evening, calm and free, 



The holy time is quiet as a Nun 



Breathless with adoration ; the broad sun 



Is sinking down in its tranquillity ; 



The gentleness of heaven broods o'er the sea : 



Listen ! the mighty Being is awake 



And doth with his eternal motion make 



A sound like thunder everlastingly. 



The use of the imagination in science has evoked 

 criticism, not so much in the mind of the general public 

 as in that of scientific men themselves. The passage, in 

 a majestic swoop of almost boundless extent, from the 

 known to the unknown is felt to be travelling so far out- 

 side present, and even possible, experience as to run the 

 risk of losing that sure foothold on the solid ground of 

 phenomena from which the daring leap was made; it 



