136 LIGHT SCIENCE FOR LEISURE HOURS. 



structure. Multitudinous streaks, some few straight, 

 but most showing curvature more or less complex in 

 character, extended from the edge of the sun, and gave 

 to the corona the appearance of luminous hair waved 

 wildly by the wind. (It will, of course, not be sup- 

 posed that the coronal streamers were actually moving.) 

 Again, the spectroscope showed that a portion of the 

 coronal substance shone with special colours, indicating 

 its partial gaseity. The interior and brighter portion, 

 to a height of nearly 300,000 miles, shone visibly with 

 three of the four tints belonging to glowing hydrogen, 

 and, doubtless, actually with the fourth, though it 

 could not be recognised. Messrs. Lockyer and Janssen, 

 on that occasion, following a method of observation 

 suggested by Professor Young in 1870, saw not the 

 three lines (only) of these colours, but the three 

 coloured images of the corona. They dispensed with 

 the slit, which allows only a fine thread of light to be 

 examined, and simply looked at the corona through the 

 battery of prisms. The dispersive action of the prisms 

 divided the single image seen directly into three, 

 showing a red image in one direction, a blue image in 

 another, and between these, nearer to the latter, a 

 green image. Lastly, in 1871, the corona was not 

 very bright. But on July 29 the corona had shrunk 

 greatly in dimensions, and had increased correspond- 

 ingly in brightness. It extended to ordinary tele- 

 scopic vision only about 70,000 miles from the sun's 

 surface, which is considerably less than the height of 

 many prominences which have been seen on former 



