THE NEW COSMOLOGY 



opposite point of its apparent circle about the pole- 

 star. Half the sum of these angles gives the latitude 

 of the place of observation. 



As illustrating the accuracy of Tycho 's observations, 

 it may be noted that he rediscovered a third inequality 

 of the moon's motion at its variation, he, in common 

 with other European astronomers, being then quite 

 unaware that this inequality had been observed by an 

 Arabian astronomer. Tycho proved also that the 

 angle of inclination of the moon's orbit to the ecliptic 

 is subject to slight variation. 



The very brilliant new star which shone forth sud- 

 denly in the constellation of Cassiopeia in the year 

 1572, was made the object of special studies by Tycho, 

 who proved that the star had no sensible parallax 

 and consequently was far beyond the planetary regions. 

 The appearance of a new star was a phenomenon not 

 unknown to the ancients, since Pliny records that 

 Hipparchus was led by such an appearance to make 

 his catalogue of the fixed stars. But the phenomenon 

 is sufficiently uncommon to attract unusual attention. 

 A similar phenomenon occurred in the year 1604, 

 when the new star in this case appearing in the 

 constellation of Serpentarius was explained by Kep- 

 ler as probably proceeding from a vast combustion. 

 This explanation in which Kepler is said to have 

 followed Tycho is fully in accord with the most recent 

 theories on the subject, as we shall see in due course. 

 It is surprising to hear Tycho credited with so startling 

 a theory, but, on the other hand, such an explanation is 

 precisely what should be expected from the other 

 astronomer named. For Johann Kepler, or r as he 



VOL. II. 6 



