VARIABLE STARS. 11^ 



lU brightuess at its minimum keeps tlie mean between v and v of the 

 same constellation; in the maximum it does not quite reach that of ?^ 

 It takes 4d. 21h. to attain its full brightness, and 5d. 6h. for its diminu 

 tion. 



(22) /? Pegasi, R. A. 344° 7', Deck 4-27° 16'. Its period is pretty 

 well ascertained, but as to the course of its variation of light nothing can 

 as yet be asserted. 



(23) Pegasi E., E. A. 344° 47', Deck +9° 43'. 



(24) Cancri S., E. A. 128° 50', Deck -}-190 34'. 

 Of these two stars nothing at present can be said. 



Fr. AaGELXNDEU, 



Bonn, August, 18SI. 



Variation of Lic^ht in Stars whose Periodicity is 

 Unascertained. — In the scientific investigation of important 

 natural phenomena, either in the terrestrial or in the sidereal 

 sphere of the Cosmos, it is imprudent to connect together, 

 without due consideration, subjects which, as regards their 

 proximate causes, are still involved in obscurity. On this 

 account we are careful to distinguish stars Vvdiich have ap- 

 pet.red and agam totally disappeared (as in the star in Cas- 

 siopeia, 1572) ; stars which have newly appeared and not 

 again disappeared (as that in Cygnus, 1600) ; variable stars 

 with ascertained periods (Mira (3eti, Algol) ; and stars whose 

 intensity of light varies, of whose variation, however, the pe- 

 riodicity is as yet unascertained (as 7] Argus). It is by no 

 means improbable, but still does not necessarily folloVv% that 

 these four kinds of phenomena^^ have perfectly similar causes 

 in the photospheres of those remote suns, or in the nature of 

 their surfaces. 



As we commenced our account of new stars with the most 

 remarkable of this class of celestial phenomena — the sudden 

 appearance of Tycho Brahe's star — so, influenced by similar 

 considerations, we shall begin our statements concerning the 

 variable stars whose periods have not yet been ascertained, 

 with the unperiodical fluctuations, in the light of?/ Argus, 

 which to the present day are still observable. This star ia 

 situated in the o-reat and mafrnificent constellation of th« 



* Newton (Philos. Nat. Principia Mathem., ed. Le Sem' et Jacquier, 

 1760, torn, iii., p. G71) distinguishes only two kinds of these sidereal 

 phenomena. " Stellaj fixa? quoe per vices apparent et evanescunt, qure- 

 que paulatim crescunt, videntur revolvendo partem lucidam et partem 

 obscuram per vices ostendere." The fixed stars, which alternately ap 

 pear and vanish, and which gradually increase, appear by turns to shovs 

 an illuminated and a dark side. This explanation of the vai'iation of 

 light had been still earner advanced by Eiccioli. With respect to tha 

 caution necessary in predicating periodicity, see the valuable remarks 

 ol ?.ir John Herschel. in liis Ob nervations at. the Cape, ^ 201, 



K ? 



