THE THEORY OF THE HEAVENS. 133 



coming to them. Now, because the sun in turning round 

 its axis, impressed its motion equally on these vapours 

 thus detached from its surface, they preserved a certain 

 impetus to a revolving movement, whereby, according 

 to the laws of the central forces, they tended to inter- 

 sect the prolonged equatorial plane of the sun in the 

 circle in which they move ; and hence, because they press 

 to it in equal quantities from both hemispheres, they 

 accumulate there with equal forces and form an expanded 

 plain in the plane of the solar equator. 



But, notwithstanding this resemblance with Saturn's ring, 

 there remains an essential distinction which makes the 

 phenomenon of the Zodiacal Light very different from it. 

 The particles of the ring maintain themselves by the move- 

 ment of rotation implanted in them, in a free circular 

 orbit; but the particles of the Zodiacal Light are maintained 

 at their distance by the force of the sun's rays, without 

 which the motion inherent in them from the rotation 

 of the sun would be quite insufficient to keep them freely 

 revolving and from falling. For, as the centripetal force 

 of the axial rotation on the surface of the sun is not T ^ J^ 

 of the attraction, the ascending vapours would necessarily 

 have to be removed 40,000 semi-diameters from the sun 

 in order to find at that distance just such a gravitation as 

 would produce equilibrium with the motion communicated 

 to them. It is therefore certain that this phenomenon of 

 the sun is not to be assigned to it in the same way as 

 the ring of Saturn is to that planet. 



But it is not improbable that this necklace of the sun 

 may be due to the same origin which is exhibited by the 

 whole of nature, as already indicated. It may have been 

 formed out of the universal primitive matter whose particles, 



