2 30 D'lfappearance of Saturn* s Rin^ in the Year 1 803 . 



placed in Saturn. This figure, then, exhibits the exaft in- 

 clination of the plane of the ring to the ecliptic; the appa- 

 rent motion of the earth and the fun, as feen from Saturn, 

 tosjether with the time of the palfage of thcfe planets through 

 the afcending node of his ring. (See Plate V. fig. 2.) 



AB is the ecliptic feen from Saturn in the fign of Pifces, 

 and divided into degrees. The afcending node of Saturn's 

 rinor feen from thence is placed in 17^ 6\ in which point thft 

 plane of the ring interfefts the ecliptic at an angle of 31^ 20'. 

 The eye is then in that plane. Thus the ring appears as a 

 ftraisht line; «w1s the north fide, and :&^- the foulh fide of 

 it. The dotted line CD is the folar orhit feen from Saturn ; 

 and the fun's place is marked in it on the firft day of each 

 month, from November 1803 to Otlobor 1803. Thefe places 

 of the fun ai-e direftly oppofite to the heliocentric places of 

 Saturn : the longitude thusdifl'ers fix figns, and the northern 

 Jatitude of Saturn feen from thence changes into the fouthern 

 of the fun. In this manner, llio fun in Noveml)er, Decem- 

 btr, January, and to the month of June, illuminates the fouth 

 fide of the ring; but always in a fainter manner, the nearer 

 he comes to the plane of it. On the I5lh of June he pafles 

 through the plane in e. The ring^ at that time is illuminated 

 on the edge, and can be feen only by powerful telefcopes as 

 ' a fine luminous line. 



The lonsitude of the point e, reduced to the ecliptic, falls 

 in f, or 20 42' of Pifces. The fun, then, about the middle 

 of June begins to illuminate the northern fide of the ring; 

 in July, Augufi, September, Oftober, &c. he recedes more 

 and more from the plane of the ring, and the illumination of 

 it then becomes ftronger. 



The elliptical line is the earth's orbit as feen from Saturn, 

 according to its direft and retrograde motion from the ift of 

 November 1802 to the ifl. of OAober 1803, and its place is 

 marked on the firil of each month. Its longitude is fix figns 

 Jefs or more than the geocentric longitude of Saturn; and 

 the northern latitude of Saturn is changed into the fouthern 

 of the earth. 



Now, as the figure clearly fliows, the earth in November 

 and December 1^802 is reprefcntcd on the fouth fide, or 

 turned towards the fun, and therefore on the illuminated 

 fide of the ring. But afterwards the earth approaches more 

 and more to the plane of the ring; and, as the ring receives 

 -the folar rays in a more and more oblique manner, the ring 

 not only becomes narrower but even decreafes in light. On 

 the 13th of December, as may be feen by this fmail figure, 

 the earth enters the plane of the ring, and pafles to the 



northern 



