ASTRONOMY AND METEOROLOGY. 291 



heat in the interior and neighborhood of spots. An apparent de- 

 scent of a large portion of the photosphere into the interior of a 

 spot, with diminishing brightness, has been repeatedly observed ; 

 but whether the change indicates a process of cooling, or one cor- 

 responding to the transformation of clouds into invisible vapor, is 

 yet undecided. 



VARIABLE STARS. 



M. Faye, in the " Comptes Rendus," gives the following as the 

 results of his observations on variable stars : 



So-called new stars are not really so, their sudden appearance 

 being only an exaggeration of the ordinary phenomena of periodic 

 variables, corresponding to simple oscillations, more or less sen- 

 sible, in the production and maintenance of the photospheres of 

 all stars. These phenomena, considered successive when the his- 

 tory of a star is examined in part, characterize the progress of the 

 cooling of the star and the decline of its solar or photospheric 

 phase ; when they occur thus in an irregular, intermittent manner, 

 with very long and gradually increasing intervals, they are the 

 precursors of the star's extinction, or of the formation of a first 

 more or less consistent crust. Hence phenomena of this kind oc- 

 cur only in stars already very faint, and never result in the forma- 

 tion of a fine new star. 



MASS OF JUPITER. 



Herr Kriiger, from careful investigations of Themis, one of the 

 minor planets, gives the mass of Jupiter as TOTT.TB f tne snn ' s 

 mass. The mean of this and the values as given by Airy, Bessel, 

 and Jacob, is TTJ ^ -^ as the mass of the largest planetof the solar 

 system. 



NEW SOLAR EYE-PIECE. 



Messrs. Merz, of Munich, place in their solar eye-piece two 

 pairs of plane unsilvered glass mirrors in such a way that, by ro- 

 tating one pair, any part of the sun's light may be intercepted. 

 By this arrangement no false color is introduced, as with blue or 

 neutral-tint glasses. In it films are seen with a frosty tint, the 

 color of the protuberances seen in solar eclipses, which appeared 

 blue in the common oculars. 



ECLIPSE OF JUPITER'S MOONS. 



On the 21st of August, 1867, occurred the rare astronomical 

 phenomenon of Jupiter appearing without his satellites. To as- 

 tronomers this is a phenomenon of great interest, having only 

 been observed on four different occasions. It occurred in 1681, 

 and was observed by Molyneaux. Sir William Herschel saw it in 

 1802, and Wallis in 1826. It was last seen by Dawes and Gries- 

 bach in 1843. 



An eclipse of one of these satellites appears, by calculation, to 

 take place 16 minutes sooner, when the earth is in that part of its 



