V APPENDIX. 



9. "1801, April 11, 10'^ 30"°. There is a third satellite at a 

 great angle south preceding ; in the configuration it is marked 

 exactly in opposition to the second, and at half the distance of 

 the first * * * * the third by the configuration was 81*^ 

 s. p." 



On the next night Herschel examined the place where the- 

 planet was on April It, and found no star in the former place of 

 the third satellite. Herschel's satellite was in P = 1S9°, distant 

 18". Umbriel was in P = 191°27', distant 21".18. Hence 

 Herschel saw Umbriel. 



The above are all the cases which a careful examination of the 

 printed observations suggests for discussion, and it is to be re- 

 marked that of the four cases where Herschel supposed he saw 

 the interior satellites, three have been verified fully, and a reason- 

 able suspicion exists that the fourth may have been likewise a 

 veritable observation of Umbriel. A reference to the originals 

 would probably settle most of the doubts which have arisen. We 

 may conclude, then, that the elder Herschel was the first observer 

 of Ariel and Umbriel, as well as of Titania and Oberon, but 

 that he was unfortunately prevented from identifying the inner 

 satellites because his telescope could not show them on two succes- 

 sive nights. It is to be noted that Sir John Herschel never caught 

 a glimpse of them during his examination of Uranus with the same 

 telescope in 1828 and 1832 ; the extreme difficulty of these objects 

 makes us wonder at the marvellous skill and patience manifested 

 by the elder Herschel in this difficult research. 



It would be an interesting and useful research to endeavor to 

 explain Herschel's observations of the III., V., and VI. satel- 

 lites, and to show that these were observations of small stars. 

 This research I hope to execute upon the return of Prof. Watsoa 

 and Dr. C. H. F. Peters from their respective journeys for the 

 purpose of observing the transit of Yenus. Both of these astro- 

 nomers have the most extended and minute maps of all the small 

 stars in the region where Uranus was in 1787 to 1801 ; and a 

 careful examination of tracings of these maps and of Herschel's 

 observations could not fail to throw some light upon the supposed 

 discovery of satellites 111., V., and VI. 



The next observations of these objects were by Lassell and 

 0. Strave in 1817. 



Lassell's observatior\s are given in the Monthly Notices of the 

 Royal Astronomical Society, vol. viii. p. 44. I have compared 

 these with the theory as below. 



(84) 



