SECTION II. 



OBSERVATIONS OP NEW AND VARIABLE STARS. 



IT lias long been known that among the fixed stars are 

 several which experience a periodical increase and dimi- 

 nution of brightness. The star Omicron, in the constella- 

 tion Cetus, sometimes appears as a star of the second 

 magnitude, but continues of this brightness only about a 

 fortnight, when it decreases for about three months, till 

 it becomes completely invisible to the naked eye, in 

 which state it remains about five months, and then in- 

 creases again to the second magnitude, the interval be- 

 tween its periods of greatest brightness being about eleven 

 months. The star Algol varies from the second to the 

 fourth magnitude, going through its changes in less than 

 three days. More than forty such cases have been no- 

 ticed, although in many of them the change of brightness 

 is not very remarkable. 



In the case of a few stars, remarkable changes of 

 brightness have been observed, which have not been re- 

 duced to any law of periodicity. The star t\ (eta) Argus 

 is of this kind. This is a star of the southern hemisphere 

 in right ascension lOh. 39m. ; south declination 58 54'. 

 In Halley's catalogue, constructed in 1677, it is marked 



