LIGHT. 137 



were believed to prove that they have no appreciable atmos 

 pheres. 



If it be admitted, or considered proved, that the sun and 

 planets have atmospheres and little doubt now exists on this 

 point then the grounds upon which Wollaston founded his 

 arguments are untenable ; and there appears no reason why 

 the atmosphere of the different planets should not be, with 

 reference to each other, in a state of equilibrium. Ether, or 

 the highly-attenuated matter existing in the interplanetary 

 spaces, being an expansion of some or all of these atmos 

 pheres, or of the more volatile portions of them, would thus 

 furnish matter for the transmission of the modes of motion 

 which we call light, heat, &c. ; and possibly minute portions 

 of these atmospheres may, by gradual changes, pass from 

 planet to planet, forming a link of material communication 

 between the distant monads of the universe. 



The view given above would approximate the theory of 

 the transmission of light by the undulations of ordinary mat 

 ter to the other two theories, which equally suppose the non- 

 existence of a vacuum ; for, according to the emissive or 

 corpuscular theory, the vacuum is filled by the matter itself, 

 of light, heat, &c. ; according to the ethereal, it is filled by 

 the all-penetrating ether. Of the existence of matter in the 

 interplanetary spaces we have some evidence in the diminish- 

 ing periods of comets ; and where, from its highly attenuated 

 state, the character of the medium by which the forces are 

 conveyed cannot be tested, the term ether is a most appropri 

 ate generic name for such medium. 



Newton has some curious passages on the subject matter 

 of light. In the c Queries to the Optics he says : 



Are not gross bodies and light convertible into one 



another, and may not bodies receive much of their activity 



from the particles of light which enter their composition? 



* * * The changing of bodies into light and light into 



bodies is very conformable to the course of nature, which 



