1869.] 



of the Solar Prominences. 



63 



token I have been waiting many days for sunshine since I brought my ap- 

 paratus to its present state. I can only devote a single morning hour to 

 it (before breakfast), but I make a little advance every day. The dark 

 band across is a slit-image corresponding to C (aperture about 1'). Through 

 the slit, as through a screen, is seen the monochromatic image of the " chro- 



mosphere," a continuous envelope, which may be seen of nearly the same 

 width everywhere. I estimate it at 20" to 30". Through the slit comes 

 also a segment of the true limb, whose light is scattered up and down. It 

 is wanting in C-light, and therefore within the C-image of the slit is seen a 

 dark segment of the sun's limb, an inversion which nothing but "lumino- 

 logy " can enable one to understand. There are two classes of solar 

 cloud* represented here; viz. the fleecy and the well defined : in both 

 cases I have taken the liberty of seeing round the corner (so to speak), and 

 giving the whole form as it might be seen by slightly pressing on the tube. 

 "With this exception, and a like one due to my having (to avoid confusion) 

 retained a slightly stronger definition in the central parts than one actually 

 obtains when so much of the limb is seen, there is, I believe, no exagge- 

 rationf . The whole picture, of course, is to be supposed seen on a back- 

 ground of pretty strong solar spectrum ; and the vertical streaky light is 

 to be supposed just short of dazzling — as strong, in fact, as the eye can bear 

 without losing its power of distinguishing relative intensities. 



A large group of spots (of which more anon) was visible just within the 

 limb yesterday, but was not traceable to-day ; it must have gone off near 

 those horns. 



The universality of the hydrogen envelope, now beyond dispute, would 

 account satisfactorily for the dark C and F lines in solar light ; and one 

 might well rest content there; but the I (bright) line is as persistent in this 

 envelope as a and /3 (C and F) ; yet there is no trace of any absorption- 

 line, corresponding to d, in the solar light. The discrepancy between fact 



* The word has be«n objected to as inappropriate ; but so long as we may speak of 

 ■ clouds of smoke," " clouds of dust," 14 clouded vision," &c, it is crippling language to 

 object on the score of inaccuracy. 



t [The original sketch was in pencil, and the contrast between light and shade is 

 exaggerated in the woodcut. — Gr. G. S.] 



