THE CONSTITUTION OF NATUKE. 5 



once heated there, would continue for ever heated ; a 

 sun or planet once molten, would continue for ever 

 molten. For, the loss of heat being simply the ab- 

 straction of molecular motion by the aether, where this 

 medium is absent no cooling could occur. A sentient 

 being on approaching a heated body in this region,, 

 would be conscious of no augmentation of temperature. 

 The gradations of warmth dependent on the laws of 

 radiation would not exist, and actual contact would 

 first reveal the heat of an extra ethereal sun. 



Imagine a paddle-wheel placed in water and caused 

 to rotate. From it, as a centre, waves would issue in 

 all directions, and a wader as he approached the place 

 of disturbance would be met by stronger and stronger 

 waves. This gradual augmentation of the impression 

 made upon the wader is exactly analogous to the aug- 

 mentation of light when we approach a luminous source. 

 In the one case, however, the coarse common nerves of 

 the body suffice ; for the other we must have the finer 

 optic nerve. But suppose the water withdrawn ; the 

 action at a distance 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 aether; and the propagation of waves 

 through the liquid is mechanically similar to the pro- 

 pagation of light and radiant heat. 



As far as our knowledge of space extends, we are 

 to conceive it as the holder of the luminiferous aether, 

 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 



