THE CONSTITUTION OF NATURE. 3 



But suppose the water withdrawn; the action at a dis- 

 tance would then cease, and, as far as the sense of touch is 

 concerned, the wader would be first rendered conscious of 

 the motion of the wheel by the blow of the paddles. The 

 transference of motion from the paddles to the water is 

 mechanically similar to the transference of molecular 

 motion from the heated body to the ether; and the prop- 

 agation of waves through the liquid is mechanically 

 similar to the propagation of light and radiant heat. 



As far as our knowledge of space extends, we are to con- 

 ceive it as the holder of the luminiferous ether, through 

 which are interspersed, at enormous distances apart, the 

 ponderous nuclei of the stars. Associated with the star 

 that most concerns us we have a group of dark planetary 

 masses revolving at various distances round it, each again 

 rotating on its own axis; and, finally, associated with 

 some of these planets we have dark bodies of minor note 

 the moons. Whether the other fixed stars have similar 

 planetary companions or not is to us a matter of pure con- 

 jecture, which may or may not enter into our conception 

 of the universe. But probably every thoughtful person be- 

 lieves, with regard to those distant suns, that there is, 

 in space, something besides our system on which they 

 shine. 



From this general view of the present condition of space, 

 and of the bodies contained in it, we pass to the inquiry 

 whether things were so created at the beginning. Was 

 space furnished at once, by the fiat of Omnipotence, with 

 these burning orbs? In presence of the revelations of 

 science this view is fading more and more. Behind the 

 orbs we now discern the nebulae from which they have 

 been condensed. And without going so far back as the 

 nebulae, the man of science can prove that out of common 

 non-luminous matter this whole pomp of stars might have 

 been evolved. 



The law of gravitation enunciated by Newton is, that 

 every particle of matter in the universe attracts every 

 other particle with a force which diminishes as the square 

 of the distance increases. Thus the sun and the earth 

 mutually pull each other; thus the earth and the moon 

 are kept in company; the force which holds every respec- 

 tive pair of masses together being the integrated force of 

 their component parts. Under the operation of this force 



