Manchester Memoirs, Vo/. Iv. (191 1), No. 14. 



XIV. On the Periodic Times of Saturn's Rings. 

 By Henry Wilde, D.Sc, D.C.L., F.R.S. 



Ruei-c'cd and Read .Ipril jj;f/i. rgj i . 



In my paper on the " Origin of Cometary Bodies and 

 Saturn's Rings," read before the Society in October last,* 

 a new determination was made of the periodic times of 

 the rings, based on the commonly accepted distance of 

 Mimas, y^G Saturnian units. This element of the orbit 

 was derived from observations made by Herschel and 

 subsequently adopted by all astronomical writers. 



Recent observations of American astronomers with 

 more powerful telescopes and under more favourable con- 

 ditions, have reduced the distance of Mimas from the 

 planet to 3* 16 units, with the consequent increase in the 

 times of rotation of the rings. 



The difference between the older and later determina- 

 tions is sufficiently large to induce me to place on record 

 for comparison the results computed from both observa- 

 tions and Kepler's third law, as shown and demonstrated 

 in the following tables : — 



Distances of Mimas = 3*36 and outer edge of ring A = 2'3. 

 CO yZ^' '• 2"3'' : : 22h. 37'm. ; x= I2h. 48-m. for A. 



Distances of Mimas =3"36 and inner edge of ring C= i'27. 



(2) i'i6' : V2f : : 22h. 37''m. : x=^\\. 15'm. for C. 



Distances of Mimas =3'i6 and outer edge of ring A = 23. 



(3) 3"i6' : 2-3' ; : 22h. 37-m. : x— i4h. 4-m. for A. 



Distances of Mimas = 3*16 and inner edge of ring Q= 127 



(4) 3-I6'' ; 1-27' : : 22h. 37-m. : ,r=5h. 45'm. for C. 



* Manchester Memoirs, vol. 55, 1910-II. 



May 8th, igii. 



