APPENDIX. IV 



true, brings it 34° from the parallel, but we must remember that 

 in the first place the angle of position was merely an estimate, 

 and secondly, that " following" is here shown by Herschel him- 

 self to have been but a rough terra, not indicating an angle of 

 position of exactly 90°. 



The " fourth satellite" of this night was proved to have been 

 a star. 



3. "1Y90, Jan. 20, 12'' 5" * * * * a third satellite is 

 45° n. p. in a line with the planet and second satellite." 



Umbriel had a position angle of 301°, and was distant 13". 72; 

 Ariel was n. f. ; Oberon (the "second satellite") was in P = 324° 

 €8', and we must again conclude that Umbriel was seen. 



4. "1193, Feb. 5, 9'' 18>" * * * * a very small star is 

 19° 3' s. p. * * * * there is no subsequent observation of 

 the small star." 



Umbriel was in P = 18T° 19', and Ariel was n. p. Herschel's 

 " small star" had a position angle of 250° 57', and hence it was 

 neither Ariel nor Umbriel. 



5. "1793, March 9, 10** 35™ * * * * a third (satellite) 

 is about 65° s. p." 



Umbriel was n. p. and Ariel was n. f., and hence this observa- 

 tion refers to neither of them. 



6. "1794, Feb. 28, 91^ 43'". * * * * There is a small 

 star * * * * about 24° n. f " 



Both Ariel and Umbriel were n. p., and hence the small object 

 was a star. 



7. " 1 794, March 27. A supposed third of this evening is pre- 

 ceding the first satellite, but nearer the planet * * * * The 

 first satellite was 79° n. f." 



Titania (the "first satellite") was in P = 10° 20', distant 

 34".43, while Ariel was in P = 20° 48', and distant 13".48, 

 Umbriel being at this time s. f. Hence we must conclude that 

 Herschel saw Ariel. 



8. ' 1798, Feb. 15, 12'' 13™ * * * * position of the 

 supposed fifth satellite" (which was really Oberon) "84° 49' n. f." 

 * * * * at " about half the distance of the second satellite," 

 and between it and the planet, Herschel saw what "must have 

 been an interior satellite at its greatest northern elongation." 

 Oberon was in P = 14° 46', distant 32".00 ; Ariel was'in P = 

 213° 7', distant 5". 06, and therefore invisible; Umbriel was in 

 P = 194° 26', distant 18". 99, and therefore in its most favorable 

 position. Herschel says the interior satellite was between Oberon 

 and the planet, and if this is so he did not see Umbriel. His 

 account of this night's work (op. cit., pp. 332-3 and 359) is con- 

 fused, and leads to the suspicion (no more) that an examination 

 of the originals might prove his position of the interior satellite 

 180° wrong — in which case Umbriel would have been seen. As 

 it is we must suppose the contrary. 



(33) 



