THE STELLAR UNIVERSE. 



N.B. In the above list the letters B. A. C. indicate the catalogue of the 

 British Association, B. the catalogue of Bode. Numbers before the name 

 of the constellation (as 34 Cygni) denote Flamsteed's stars. Since this 

 Table was drawn up, four additional stars, variable from the 8th or 9th 

 magnitude to 0, have been communicated to us by Mr. Hind, whose places 

 are as follow : (1.) R. A. l h 38 m 24 s ; N. p. D. 81 0' 39" ; (2.) 4 h 50 m 

 42 s , 80 6' 36" (1846); (3.) 8 h 43 m 8 s , 86 11' (1800); (4.) 22 h 12 m 9% 

 82 59' 24" (1800). Mr. Hind remarks that about several variable stars 

 some degree of haziness is perceptible at their minimum. Have they 

 clouds revolving round them as planetary or cometary attendants ? He 

 also draws attention to the fact that the red colour predominates among 

 variable stars generally. The double star, No. 2718 of Struve's Cata- 

 logue, R. A. 20 h 34 p. B. 77 54', is stated by Sir John Herschel 

 to be variable. Captain Smyth (Celestial Cycle, i. 274) mentions also 

 3 Leonis and 18 Leonis as variable, the former from 6 in to 0, Period 78 

 days, the latter from 5 m to 10'", Period 311 d 23 h , but without citing any 

 authority. Piazzi sets down 96 and 97 Virginis and 38 Herculis as 

 variable stars. 



In the case of many of the stars in the preceding Table, the 

 variations of lustre are subject to considerable irregularities. 

 Thus No. 13 was scarcely visible from 1698, for the interval of 

 three years, even at the epochs when it ought to have had its 

 greatest lustre. The extremes of lustre of No. 9 are also very 

 variable and irregular. In general the variations of No. 22 

 are so inconsiderable as to be scarcely perceivable, but they 

 become sometimes suddenly so great that the star wholly disap- 

 pears. The variations of No. 25 were very conspicuous from 

 1836 to 1840, and again in 1849, being much less so in the 

 intermediate time. 



44. Several explanations have been proposed for these ap- 

 pearances. 



1. Sir TV. Herschel considered that the supposition of the 

 existence of spots on the stars similar to the spots on the sun, 

 combined with the rotation of the stars upon axes, similar to 

 the rotation of the sun and planets, afforded so obvious and 

 satisfactory an explanation of the phenomena, that no other need 

 be sought, 



2. Newton conjectured that the variation of brightness might 

 be produced by comets falling into distant suns and causing 

 temporary conflagrations. Waiving any other objection to this, 

 conjecture, it is put aside by its insufficiency to explain the 

 periodicity of the phenomena. 



3. Maupertius has suggested that some stars may have the form 

 of thin flat disks, acquired either by extremely rapid rotation on 

 an axis, or other physical cause. The ring of Saturn affords an 

 example of this, within the limits of our own system, and the 



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