( 'ZU ) 



eclipse observations need coiifinnatioii froni observations of eelipses.*) 



V. Alt'dii loiKjitndi's (iiul niciiii, niotioiis. 



The correct ioj IS to the mean lungitndes on J 900 .Ian. 0.0 of the 

 three inner satellites have been determined together with the libration, 

 and the residnals have already been given in Table IV. For the 

 fonrth satellite the adopted correction is — O^^.O^O, and t lie residuals 

 are given in Table V. 



TABLE V ^ / 



If the corrections are added to the values adopted in computing 

 the tal»ular places, and then referred to the tirst })oint of Aries h\ adding 

 the adopted longitude of the point (J, we tind for 1900 Jan. 0, 

 mean Greenwich noon, the values which are given below, sub I. 



Iji the introduction to his tables Damoiseau states the mean longi- 

 tudes for 1750 Jan. 0.5, mean time of Paris. If we consider these 

 as being derived directly from the obser\ations, they requii-e a small 

 correction, since Damoiseau has used the value 493^2 of the light- 

 time, while in the reduction of the modern observations the value 

 498\46 was adopted. If Damoiseau had adopted this latter \alue, he 

 would have found the same longitudes for an epoch which is 5^26 X ^ 

 earlier, L being the mean distance of Jupiter. The observed mean 

 longiiudes, in order to correspond correctly to the tabular epoch, 

 therefore require the correction '^) : 

 5.26 

 ■ 86400 ^ 



^) It has also been pointed out in Gron. Publ. 17 that the series of extra- 

 eclipse observations from which the libration was derived, not being made for 

 this special purpose, does not in every respect fulfil tbe conditions necessary for a 

 good determination of the libration. 



~) In Gron. Publ. 17 I assumed, on the authority of Gookson, Gape XII. 3, 

 page 56, that Marth's longitudes for 1750.Ü were identical with Damoiseau's. 

 This, however, they are nol, Marth having applied the correction for Ihe change 

 in the adopted constant of al)erraliou with the wrong sign. This was pointed out 

 to me bv Mr. Banacuiewicz. 



