184 SPECIAL RESULTS IN THE URANOLOGICAL PORTION 



The belief in the existence of non-luminous stars was 

 already prevalent in Grecian antiquity, and especially in the 

 early times of Christianity. It was assumed that " among 

 the fiery stars which are nourished by vapours, there move 

 other earthy bodies which remain invisible to us." ( 301 ) The 

 entire extinction of new stars, particularly of those in Cas- 

 siopeia and Ophiuchus, so carefully observed by Tycho Brahe 

 and Kepler, appeared to afford a firmer support to this 

 notion. As it was then supposed that the first-named of 

 these two stars had already shone forth twice before, at 

 intervals of about 300 years, the idea of annihilation or 

 complete dissolution was not likely to find acceptance. The 

 illustrious author of the "Mecanique Celeste" founds his 

 persuasion of the existence of non-luminous masses in the 

 Universe on the same phenomena of 1572 and 1604. 

 "Ces astres devenus invisibles apres avoir surpasse Feclat 

 de Jupiter mme, n'ont point change de place durant leur 

 apparition." (Only the luminous process in them has 

 ceased.) "II existe done dans 1'espace celeste des corps 

 opaques aussi considerables et peut-tre en aussi grands 

 n ombres que les 6toiles". ( 302 ) So also Madler, in his 

 " Untersuchungen iiber die Fixstern-Systeme" ( 303 ) says, 

 " A dark body might be a central body ; it might, like our 

 sun, be only surrounded in its immediate vicinity by dark 

 bodies such as are our planets. The movements of Procyon 

 and Sirius pointed out by Bessel constrain (?) the assump- 

 tion that there are cases in which luminous bodies are 

 satellites to dark masses." I have already noticed that 

 some adherents of the emanation-theory of light supposed 

 such masses to be light-radiating, though at the same time 

 invisible from being of such enormous dimensions that the 



