190 OUTLINES OF NATURAL PHILOSOPHY. 



observed between the ring and the planet9.*SM5TH's 

 Optics. DE LA LANDE, torn. HI. 3353. 



t>. The plane of the ring is in the plane of the equator 

 of Saturn 5 it is inclined to the orbit of the pla- 

 net, nearly at an angle of 30, and remains always 

 parallel to itself. 



196. When Saturn is in the longitude of 5 s 

 0, or 11 s 20, the plane of the ring passes 

 through the Sun, and the light then falling up- 

 on it edgewise, it is no longer visible to us. 



a. This disappearance of the ring has been often ob- 

 served. LA LANDE, 3354. 



The disappearance of the ring from this cause, lasts 

 only a few days ; for when Saturn has passed the 

 node of the ring three or four minutes, or the Sun 

 has risen above its plane by that quantity, the ring 

 becomes visible, 



~ 



. 

 197 The ring also disappears, when its plane 



passes through the Earth ; for its edge, or its 

 thickness, being then directed to the eye, and 

 being too fine to be seen, the planet appears 

 quite round. 



a. In this case, the Earth requires to be elevated above 

 the plane of the ring, at least half a degree, before 

 the ring is seen, which makes it continue invisible 



sevejr 



