THE INTERSTELLAR ETHER 



diation of something else which is not material, 

 operate upon and affect other matter not in contact, as 

 it must do if gravitation in the sense of Epicurus be 

 essential and inherent in it ... That gravity should 

 be innate, inherent and essential to matter, so that 

 one body can act upon another at a distance, through 

 a vacuum, without the mediation of anything else, by 

 and through which their action and force may be 

 conveyed from one to another, is to me so great an 

 absurdity that I believe no man who has in philo- 

 sophical matters a competent faculty of thinking can 

 ever fall into it." He sought for the explanation of 

 gravitation in the existence of an ethereal medium at 

 an early date, but found that he was not able from 

 experiment or observation to give a satisfactory ac- 

 count of this medium and the manner of its operation 

 in producing this, the chief phenomena of nature.* 



The lapse of nearly two hundred years has left the 

 problem of the nature of the ethereal medium still 

 unsolved, and even the possibility of its non-exist- 

 ence, and of the action at a distance of matter upon 

 matter, has still its advocates ; so far at least as the 

 cause of the weight of matter or gravitation is con- 

 cerned. 



The recognition of the fact that radiant heat, 



* Enc. Brit. 9th Ed. Art Attraction. 

 119 



