JQ FIGUKE OF THE TLANET SATUJIN. 



OWervaiions on June 2. I viewed Jupiter and Saturn alternately with a 



Saturn, l.y maorni tVinrr power of only 500, that the convexity of tl>e 

 which Its lingu- o ,' b I . ' j r j i r 



lar lisuie is ai- C) e-glafs might occafion no deception, and tound tlie torni 

 certalncd. „j- t|,e i^^q planets to difler in the manner that has been de- 



fcribed. 



Wid) 200 I faw the difference very plainly ; and even with 

 160 it vvas fufficieiidy vilibie to admit of no doubt. Thefe low 

 powers fliow the figure of the planets perfecliy well, for as 

 the field of view is enlarged, and the motion of the objefils in 

 pairing is lelFened, we are more at liberty to fix our attention 

 upon them. 



I compared the telefcopic appearance of Saturn with a figure 

 drawn by the meafures I have taken, combined with the pro- 

 portion between the equatorial and polar diameters determined 

 in the year 1 7 89 ; * and found that, in order to be a perfect 

 refemblance. my figure required fome fmall reduction of the 

 longeft diameter, fo as to bring it nearly to agree with the 

 meafures taken the 27th of May. When I had made tlie ne- 

 ccfiary alteration, my artificial Saturn was again compared 

 with the telefcopic repreientation of the planet, and I was then 

 fati^fied that it had all the correc^nefs of whicli a judgment of 

 the eye is capable. An exa6l copy of it is given in Plate IX. 

 The dimenfions of it in proportional parts are, 



The diameter of the greateft curvature - 36 

 The equatorial diameter - - - - 35 

 'J'he polar diameter - - - • - 32 



Latitude of the longed diameter - 43** 20.' 



iiw 



The foregoing obfervations of the figure of the body of 

 Saturn will lead to fome intricate refearches, by which the 

 quantity of matter in the ring, and its folidity, may be in fome 

 meafure afcerlained. They alfo afford a new inftance of the 

 effect of gravitation on the figure of planets; for in the cafe 

 of Saturn, we fnall have to confider the oppofite influence of 

 two centripetal and two centrifugal forces: the rotation of both 

 the ring and planet having been afcertained in fome of my 

 former Papers. 



* See Phil. Tr:mf. for 1700, page. IT. 



fads 



