( il5 ) 



liis results. In consequence of liiis error we must read for tlie longitude 

 east of Greenwich of the observiui;' phice on the ground of our 

 dwelling house, as given on p. (i04 3''41'"48\()(i instead of 48^11. 



Taking into account the corrections mentioned above, the list of 

 results connnunicated in the Proceedings of March (p. 607 of the prece- 

 ding \olume) must be moditied as gi\'en at the end of this paper; 

 see tallies la and I^, 



We then find as correction of Germain's longitude: 



Using disapp. and reapp. inditferently . . — 2^90 d= 0^64 (m. error) 

 Treating them separately — 0.81±1.22(„ „ ) 



It is much to be i-egretted we did not succeed in observing more 

 reappearances. There is always a greater chance to observe the 

 disai)pearances than the reap])earances at the dark limb of the moon. 

 A short time after ]iew^ moon until a few days after first quarter 

 we can easily see with a good telescope on the east side of the 

 moon stars of the 8^'', 9''' or perhaps even the ^^^^^^ magnitude, of 

 which the disappearance nia^' be easily obserx ed ; no preparation 

 is required for this. 



For the observation of reappearances at the dark limb, a prepa- 

 i-ation b}' means of star maps is necessary, which takes up much 

 time. We must calculate froui hour to hour the parallax of the 

 moon in R. A. and declination and hence dej'ive its apparent places, 

 draw them on the map, and then derive geometrically the instants 

 at which the stars considered must reappear. For the most southern 

 declinations the star ma|)S themselves had to be constructed first by 

 means of Argklandkr's southern Zonae. Moreover it is always desirable 

 finally to derive more accurate results by a cak'ulalion according 

 to the know]i formulae. 



The operations described here have been executed as well for the 

 days preceding full moon as for those following it, and it was oni- 

 bad luck that in the latter part of the lunation the weather was 

 always unfavourable. 



After this revision of the calculations a small negative correction 

 of the longitude of St. Denis according to Germain seems probable, 

 although its exact amount is uncertain. We have however, still to 

 consider wiiat follows : 



When in 1884 Auwers wanted to determine a fundamental meridian 

 for Australia^), for which purpose he chose that of Sydney, he 

 used 78 occnltations observed from 1873 to 1870 in Windsor (N. 



1) Astron. Nadir. Vol. 110 p. 289—346. 



