of the Heavenly Bodies. 13 



correcting some very important errors of great authority, dis- 

 posing of the supposed anomaly of the repulsion of light by 

 bodies, and of that repulsion being changed at other distances 

 into attraction, by pointing out the bodies whose attractions 

 had been mistaken for the repulsions of other bodies, and thus 

 referring all the appearances to the single and simple principle 

 of attraction. These inflections exist in the same continuous 

 medium, refractions never but at the discontinued confines of 

 different media. These inflections, in the continuous medium 

 of air, produce all the preceding observed changes of the 

 heavenly bodies. 



In imperfectly transparent media, as opals, rubies, coloured 

 glasses and tinctures, various particles are diffused throughout 

 the bodies, which by their inflections change the directions and 

 colours of the light at varying thicknesses. Such a continuous 

 medium is the atmosphere; transparent in itself, imperfectly 

 transparent in consequence of the floatage of various particles 

 of other bodies throughout and between its parts. 



At the confines of any two adjacent transparent bodies, there 

 is a discontinuity, and separation to definite intervals, of the 

 particles of both, dependent upon the relative attractions of 

 the particles of each body, for themselves, and for the particles 

 of the other body; which attractions, although they prevent 

 guch an intimate union of the bodies as would end the reflective 

 and refractive powers of both, does not altogether cease to 

 exist between the neighbouring particles of each fbr the other ; 

 and there is one class of transparent continuous bodies, between 

 whose particles there exist in given lines of direction, intervals 

 of aggregation similar to the intervals between different media, 

 which although the bodies cease not to be continuous aggre- 

 gates, yet, at these intervals, a division of the light takes 

 place, similar to that between different transparent bodies, and 

 produces a double refraction within the bodies, in lines duly 

 related to these and other lines of aggregation. This original 

 conjecture respecting the causes of the double refractions of 

 certain crystals, was happily confirmed by the splendid dis- 

 coveries of Malus, who observed that a polarization also takes 



