180 SPECIAL RESULTS IN THE URANOLOGICAL PORTION 



200 calculated comets, of which 5 are of short periods of 

 revolution, and interior, i. e. their paths are entirely com- 

 prised between those of the principal planets. During 

 their mostly short appearance, they, or rather those amongst 

 them which are visible to the naked eye, as well as the true 

 planets, and those bodies which have suddenly shone forth 

 as new stars of the first magnitude, animate, in the most 

 attractive manner, the already rich picture of the sidereal 

 heavens. 



The knowledge of the proper motion of the fixed stars is 

 wholly connected, historically, with the advances which have 

 been made in the art of observing by the improvement of 

 instruments and of methods. It first became possible to 

 discover these motions when telescopes were combined with 

 graduated instruments, when astronomers were able pro- 

 gressively to advance from certainty in respect to a minute of 

 arc (which Tycho Brahe first succeeded, by the most strenu- 

 ous endeavours, in giving to his observations in the Island 

 of Huen), to certainty in respect to seconds and parts of 

 seconds, and when it was possible to compare together re- 

 sults separated by a long series of years. Such a comparison 

 was made by Halley, who employed in it the positions of 

 Sirius, Arcturus, and Aldebaran, as entered by Ptolemy in 

 his Hipparchian Catalogue, 1847 years before. He thought 

 himself justified by this comparison (1717) in announcing 

 the existence of a proper motion in the three above named 

 fixed stars. ( 291 ) The great and deserved regard which, even 

 long after Flamsteed's and Bradley* s observations, was paid 

 to the Eight Ascensions contained in Burner's Triduum, 

 incited Tobias Mayer (1756), Maskelyne (1770), and Piazzi 

 (180(1), to compare Homer's observations with later ones.( 292 ) 



