SUNS IN YOUTH AND OLD AGE 133 



the brightness changed from year to year, or from 

 age to age. By this method actual inspection would 

 at once decide whether a star was increasing or 

 diminishing in brightness compared with other stars. 

 It was an attempt to ascertain the advance of life 

 or the vigour of youth, the beginnings of decay or 

 the promise of a long continuance of brightness 

 among the countless suns in creation. Of the import- 

 ance of these investigations he entertained no doubt, 

 nor should we. " The great number of alterations of 

 stars that we are certain have happened within the 

 last two centuries, and the much greater number 

 that we have reason to suspect to have taken place," 

 are curious features in the history of the heavens, 

 as curious as the slow wearing away of the landmarks 

 of our earth on mountains, on river banks, on ocean 

 shores. " If we consider how little attention has 

 formerly been paid to this subject," he goes on to 

 say, " and that most of the observations we have 

 are of a very late date, it would perhaps not appear 

 extraordinary were we to admit the number of 

 alterations, that have probably happened to different 

 stars, to be a hundred ; this compared with the number 

 of stars that have been examined, with a view to 

 ascertain their changes, which we can hardly rate 

 at three thousand, 1 will give us a proportion of 1 to 



1 The most ancient catalogue of the stars is that of Ptolemy (140 A.D.) 

 of Alexandria, which was probably a revised transcript of that of 

 Hipparchus (160 B.C.). It contains 1022 stars. Tycho's catalogue 

 (1572 A.D.) contains 777 principal stars, to which Kepler afterwards 

 added 280, taken probably from Tycho's own manuscripts. Hevelius 

 (1690 A.D.) published a catalogue containing 950 stars of former lists, 

 603 observed by himself, and 377 southern stars observed by Halley 

 from Saint Helena. "But the most perfer-t and the largest catalogue 



