Nov. 12, 1885] 



NATURE 



37 



this perhaps induced observers to imagine that they were 

 not true solar appendages. Independently and nearly 

 simultaneously Janssen and Lockyer showed that these 

 red flames may be rendered visible on ordinary occasions 

 by means of the spectroscope, and they are now the daily 

 study of solar observers. It has been shown that they 

 consist chiefly of incandescent hydrogen, and the reason 

 is very obvious why we cannot see them without the 

 spectroscope. The glare of light around the sun's disc 



sisting of rays of a great many refrangibilities which are 

 spread out into a long ribbon by the spectroscope, and 

 consequently diluted. On the other hand, that from the 

 red flames consists only of one or two widely-separated 



refrangibilities which are not spread out, and therefore 

 not diluted. The consequence is that the red flames 

 give us a few bright spectral lines standing out in a solar 



Dl D? 



(a strictly tenestrial phenomenon due to reflexion) is in 

 general so strong compared to the light from the red 

 flames, that it is impossible for the eye to distinguish 

 the latter. Now during a total eclipse this glare is re- 

 moved, and hence the eye can see the red flames. But 

 in the spectroscope we have a means not so much of 

 removing as of diluting the glare, while at the saine time 

 the light from the red flames is not diluted. This arises 

 from the fact that the glare is ordinary sun-light, con- 



spectrum so diluted as to be almost invisible, 

 we have a representation of the eclipsed sun 

 red flames near the sun, and the corona ex 

 great distance around his disc : while in Fi 



In Fig. 15 



showing the 



tending to a 



16 we have 



19. — Exhibiting the sp 



1 of the chromosphere above and that of the photosphere belo 



an enlarged view of one of the red flames, showing the 

 curious shapes which these phenomena frequently assume. 



The application of the spectroscope by Lockyer and 

 others to selected portions of the solar disc and its sur- 

 roundings has been most fruitful in its consequences. 



One of the first results obtained by Lockyer was the 

 arrow-shaped appearance of the bright line F of the 

 sun's atmosphere, when the slit of the spectroscope is 

 made to form a continuation outwards of the solar radius ; 

 that is to say, is perpendicular to the rim o^ the sun. 



I This is shown in Fig. 17, and the explanation is very 

 simple. It will be remembered that the line F of hydrogen 



I is one which is very susceptible to an increase of pressure. 

 It is therefore much wider at the bottom of the solar 

 atmosphere than at the top, thus presenting the appear- 

 ance seen in the figure. When the same observer applied 

 the spectroscope to a sun-spot there was found to be a 

 thickening of various absorption lines in the region of 



i the spot, thus indicating an increase of pressure, and 



: proving that a spot is a phenomenon that occurs below 



