OF THE COSMOS. NEW STARS. 135 



the eleventh star in the lower part of Cassiopeia's chair. 

 From December 1573 to February 1574, it diminished 

 successively to the 5th and 6th magnitudes,, In the 

 following month, after shining for seventeen months, the 

 new star disappeared altogether, leaving no trace visible 

 to the naked eye." (The telescope was invented thirty-seven 

 years later.) 



It appears, then, that the loss of light in this star was 

 exceedingly gradual and regular, and not interrupted by 

 periods of renewed or fresh increase of light, (as has been 

 several times the case in our own days with TI Argus, which, 

 indeed, is not to be called a new star). In the star 

 in Cassiopeia, of which we have been speaking, there was 

 alteration of colour as well as of light, a circumstance 

 which has since given occasion to many erroneous conclu- 

 sions respecting the velocity of coloured rays in traversing 

 space. When it first appeared, and as long as it equalled 

 first Venus and then Jupiter in brightness, its light was, 

 during two months, white; after which it passed through 

 yellow into red. In the spring of 1573, Tycho Brahe com- 

 pared it to Mars ; he next found it almost comparable to 

 the star in the right shoulder of Orion (Betelgeuze) . Its 

 colour resembled most nearly the red colour of Aldebaran. 

 In the spring of 1573, particularly in the month of May, 

 the whiteness returned (albedinem quandam sublividam 

 induebat, qualis Saturni stellse subesse videtur). In 

 January 1574 it still continued to be of the 5th magnitude 

 and white, but of a duller white, and with a degree of 

 scintillation strikingly great in proportion to its feeble light, 

 until its entire gradual disappearance in the month of 

 March, 1574. 



