XXIV GEELMUYDEN. ASTRONOMICAL OBSERVATIONS. [NORW. POL. EXP. 



in error, especially for the outer Satellites, it was thought at first that a suffi- 

 cient number of the more than 80 phenomena observed on board the Fram 

 would be found to have been observed also in other places with known longi- 

 tudes, in which case the error of theory could be eliminated. But only a few 

 such cases could be found, and in two of these is turned out that the same 

 phenomenon had been observed in 2 or more places in Europe, but with such 

 discordances that evidently no reliable result could be obtained in this way. 



But as a great number of observations made in Europe and Australia in 

 the years 1893 96 have been published it was thought possible to utilise the 

 whole mass as a means of deducing empirical corrections to the predicted 

 times for the periods of observation on board the Fram. This has been 

 tried in the manner explained hereafter. 



It should be stated that the imperfection of prediction is not so much due 

 to theory proper ; for the theory of LAPLACE with the small additions of SOUIL- 

 LART and ADAMS would certainly be amply sufficient; but the difficulty is with 

 the determination of the numerous constants, required by theory, but neces- 

 sarily deduced from observations. In this respect nothing has been done, so 

 for as I know, since the times of DELAMBRE and DAMOISEAU ; at all events the 

 predictions of the Nautical Almanac are based on the Tables of Damoiseau, 

 continued and corrected, for Tables I and III, by Adams (Scientific Papers, 

 Vol. I, p. 113). But the old determination of the constants is far from satis- 

 factory. Thus Damoiseau states in the introduction to his Tables that the 

 adopted value of the inclination of Jupiter's equator to his orbit, 3 4' 5", was 

 determined from observations of eclipses of Sat. Ill, but that Sat. IV gave 

 another value, smaller by 2' 47", and that this smaller value has been used 

 for this Satellite. In this connection it may be remarked, that if the coeffi- 

 cient of the equation tabulated in Damoiseau's Table XXIII for Sat. IV be 

 multiplied by 1.015, corresponding to an augmentation by 2' 47" of the said 

 angle, the eclipse of 1895 January 17, which was predicted to have a dura- 

 tion of more than half an hour, would disappear; and in point of fact the 

 Satellite was observed by Mr. Scott-Hansen during a large part of the pre- 

 dicted time of eclipse without any sensible diminution of its brightness. Of 

 course I do not mean to say that Damoiseau's Tables can be corrected in 

 this rough manner; the remark is made only to adduce an example of a 



