CHROMOSPHERE AND SOLAR PROMINENCES. 393 



spectrum will stretch athwart the field of view like a scarlet ribbon, 

 with a darkish band across it, and in that band will appear the promi- 

 nences like scarlet clouds ; so like our own terrestrial clouds, indeed, 

 in form and texture, that the resemblance is quite startling : one 

 mio-ht almost think he was looking out through a partly-opened door 

 upon a sunset sky, except that there is no variety or contrast of color ; 

 all the cloudlets are of the same pure scarlet hue. Along the edge of 

 the opening is seen the chromosphere, more brilliant than the clouds 

 which rise from it or float above it, and for the most part made up of 

 minute tongues and filaments. 



Fig. 4. 



Spectroscopic Aspect of a Prominence. 



If the spectroscope is adjusted upon the F line, instead of C, then 

 a similar image of the prominences and chromosphere is seen, only 

 blue instead of scarlet ; usually, however, this blue image is somewhat 

 less perfect in its details and definition, and is therefore less used for 

 observation. Similar effects are obtained by means of the yellow line 

 near D, and the violet line near G. By setting the spectroscope upon 

 this latter line and attaching a small camera to the eye-piece, it is even 

 possible to photograph a bright protuberance ; but the light is so 

 feeble, the image so small, the time of exposure needed so long, and 

 the requisite accuracy of motion in the clock-work which drives the 

 telescope so difficult of attainment, that thus far no pictures of any 

 real value have been obtained in this manner. 



Prof. Winlock and Mr. Lockyer have attempted, by using, in- 

 stead of the ordinary slit, an annular opening, to obtain a view of the 

 whole circumference of the sun at once, and have partially succeeded. 

 Undoubtedly, with a spectroscope of sufficient power, and adjustments 

 delicate enough, the thing can be done ; but as yet no very satisfactory 

 results appear to have been reached. We are still obliged to ex- 

 amine the circumference of the sun piecemeal, so to speak, read- 



