50 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



27th of August. The position of the object was at that time 

 in right ascension 7 minutes, and in declination north 7 53', 

 moving toward the south slowly, and of the tenth magni- 

 tude. In connection with the discovery of new planets, it 

 may be mentioned that elaborate charts of the heavens, in- 

 cluding every star visible with a large telescope, have been 

 prepared by most of the astronomers who are busy in this 

 field of discovery. Specimens of such charts were recently 

 exhibited before the German Astronomical Association by 

 Professor Peters, of Hamilton College, and the desire was ex- 

 pressed that these should be published for the general use of 

 astronomers. 



THE ECLIPSES OF JUPITER's SATELLITES. 



The method of determining the longitude at sea by obser- 

 vations of the eclipses of Jupiter's satellites, that was so dili- 

 gently studied by the great inventor of the telescope, has, as 

 is well known, during the last few years fallen into disre- 

 pute, while the advantages of the accurate observation of 

 the moon have justified navigators in generally adopting the 

 method of lunar observations in preference to any other. In 

 order, however, to remove from astronomy the reproach of 

 allowing any phenomenon to take place witliout being ob- 

 served, Professor Airy has urged that there should be made 

 more numerous observations upon the satellites of Jupiter 

 at fixed observatories, and with telescopes of various powers, 

 that the mathematical tables representing the motions of 

 these bodies might be perfected. Among the numerous con- 

 tributions to this subject that have appeared during the past 

 few years, that by Glasenapp,of the observatory at Poulkova, 

 seems to be of much interest. In this communication Glase- 

 napp compares the observations of ten different observers, all 

 stati(ined at the same place, and observing the same satellite 

 with telescopes of very various optical powers. After a care- 

 ful discussion of these results, he points out that, although 

 the differences between the individual observers are very con- 

 siderable, 3^et the mean of the observations made upon both 

 limbs of the planet accord very well among themselves, 

 whence he concludes that, although in the observation of 

 isolated contacts, the personal equations produced by the dif- 

 ferences in the eyes and telescopes may be very consider- 



