42 ON THE PERTURBATIONS OF URANUS. [2 



59. By far the most important part of these corrections arises from 



1 sJSi Y 



the term r -~ , and may therefore be immediately deduced from a com- 



nat 



parison of the observed angular motion of Uranus with that given by the 

 tables. In fact, the corrections given by this term alone for the epochs 

 above mentioned are 



Year. Hypothesis I. Hypothesis II. 



1834 +0-00447 +0-00445 



1840 +0-00694 +0-00678 



1846 +0-00853 +0-00818 



which, as we see, differ very little from the complete values just found. 

 The correction for 1834 very nearly agrees with that which Mr Airy has 

 deduced from observation in the Astronomische Nachrichten (No. 349). The 

 corrections for subsequent years are rather larger than those given by the 

 Greenwich Observations, the results of the second hypothesis, as in the case 

 of the longitude, being nearer the truth than those of the first. 



60. I made some attempts, by discussing the observations of latitude, 

 to find approximate values of the longitude of the node and inclination of 

 the orbit of the disturbing planet, but the results were not satisfactory. The 

 perturbations of the latitude are, in fact, exceedingly small, and during the 

 comparatively short period of three-fourths of a revolution are nearly con- 

 founded with the effects of a constant alteration in the inclination and the 

 position of the node of Uranus, so that very small errors in the observations 

 may entirely vitiate the result. 



61. The perturbations of Saturn produced by the new planet, though 

 small, will still be sensible, and it would be interesting to enquire whether, 

 if they were taken into account, the values of the masses of Jupiter and 

 Uranus found from their action on Saturn would be more consistent with 

 those determined by other means than they appear to be at present. The 

 reduction of the Greenwich planetary observations renders such an inquiry 

 comparatively easy, and it is to be hoped that English astronomers will not 

 be the last to avail themselves of the treasures of observation thus laid 

 open to the world. 



