SIXTH CHAPTER. 

 OF THE ZODIACAL LIGHT. 



THE sun is surrounded with a subtle vapour which sur- 

 rounds it in the plane of its equator, and is spread out to 

 only a small breadth on both sides but extending to a 

 great distance. We cannot be certain whether, as M. de 

 Mairan holds, it comes into contact with the surface of 

 the sun in the figure of a convex glass or lens (figura 

 lenticulart), or, like Saturn's ring, is everywhere removed 

 to a distance from it. Whichever of these views is correct, 

 there remains resemblance enough to bring this phenomenon 

 into comparison with Saturn's ring, and to derive it from 

 a similar origin. If this diffused matter is an efflux from 

 the sun, as is most probable, it is not possible to mistake 

 the cause which has brought it into the common plane of 

 the sun's equator. The lightest and most volatile matter, 

 which the fire of the sun raises from its surface and has 

 so raised long ago, is driven by its action far away from 

 it; and, according to the proportion of its lightness, it 

 continues to revolve at the distance at which the pro- 

 pelling action of the rays comes to equilibrium with the 

 gravity of these particles of vapour ; or, they are supported 

 by the accession of new particles which are constantly 



