452 Solar Physics. 



discovered that sun-spots have a proper motion of their own 

 " those near the solar equator moving faster than those near 

 the poles." Mr. Dawes has shown that the degrees of lumi- 

 nosity in the faculce, or bright streaks., and spots, may he 

 arranged as follows : 1, faculas ; 2, ordinary photosphere ; 

 3, the penumbra; 4, the borders of the umbra; 5, the very 

 dark central nucleus. 



When the sun suffers a total eclipse, certain red flames or 

 protuberances are noticed to surround his disc. Airy and 

 Arago first ascribed them to the sun's disc, and " Struve 

 showed it to be probable that these flames do not change 

 during the moon's motion.'" During the Spanish expedition 

 of 1860, Mr. De La Rue set this question at rest by showing 

 from his photographic pictures that the moon's motion only 

 affects these flames by covering one portion and uncovering 

 another, and he likewise demonstrated that the angular 

 motion of the flames corresponded with the theory of their 

 fixation in the sun. Secchi followed De La Rue with the 

 same results. , 



The " Willow Leaves" of Mr. Nasmyth are thus alluded 

 to in Solar Physics : — " The evidence of these is still dis- 

 puted ; but some of our best observers in this country have 

 seen them under very favourable atmospheric conditions, and 

 they have been seen more frequently by Secchi, and other 

 Italian observers." The important discovery by Ohacornac of 

 downward currents in the spots of which we have previously 

 given an account, is then adverted to, as well as a similar 

 observation by Mr. Lockyer. 



In the Kew observations, reasons have been found for 

 believing that the sun possesses an atmosphere exercising 

 refractive power. They show the central portion of his disc 

 to be more luminous than the borders. Kirchhoff and Bunsen's 

 observations on solar spectra point to the same conclusion, and 

 " the red flames which have been proved to belong to the sun 

 indicate the existence of a solar atmosphere, extending in some 

 instances as far as 72,000 miles above the photosphere. This 

 is confirmed by the light which these flames emit. Mr. De La 

 Rue has found that this light is very rich in actinic rays, so 

 much so that he was able to photograph at least one protu- 

 berance not visible to the naked eye. Now it is precisely 

 this description of light which characterizes the electric dis- 

 charge, in which gaseous matter appears in a highly heated 

 state." 



The first question which the authors of Solar Physics 

 attempt to answer is, whether the results of the observations 

 at their disposal iudicate that the umbra, or darkest part of a 

 spot, is at a lower level than its penumbra. They give tables 



