OF ARTS AND SCIENCES. 335 



Capricornus, 0,0,13; in Monoceros, 0,3,3; two in Ophiuchus, 0,14,9 ; 

 in Pe7'seus, 0,0,8 ; in Virgo, 0,0,9. 



He has made observations of the minor planets as follows : Ceres 

 (1), 6,19,28; Pallas (2), 0,0,24; Juno (3), 4,23,12; Vesta (4), 0,0,4; 

 and observed the periodical comet Pons three times in December, 

 1883, and eight times in January, 1884. 



The observations of asteroids just mentioned deserve attention, and 

 it is to be hoped that other observers will adopt the practice of observ- 

 ing such objects, and of including them in their statements with regard 

 to variable stars. The instance of lapetus shows that the variations 

 of a body sliining by reflected light may become an interesting object 

 of study, and may instruct us with regard to its period of rotation. 

 Again, supposing it to be proved, either that a certain asteroid varies 

 only in accordance with its distance from the Sun and from the ob- 

 server, or that its other variations have a sufficiently definite character 

 to allow them to be computed, it would form a valuable instrument of 

 comparison between widely separated stars. It is probable that stellar 

 magnitudes, as estimated, or even as measured by many kinds of pho- 

 tometric apparatus, are subject to systematic errors dependent upon 

 the relative frequency of stars in different parts of the sky. These 

 errors might be detected and eliminated by the comparison of aste- 

 roids with the stars differing but little from them in brightness, among 

 which they were apparently moving at different times. 



