ME. J. N. LOCKYEE ON SPECTEOSCOPIC OBSEEVATIONS OE THE SIJN. 427 
another line. As at first caught it was very long ; and by moving the telescope very 
slightly backwards and forwards in right ascension, in one direction the line shortened 
and brightened, and was visible on the solar spectrum for some distance, in another 
direction it became disconnected with the spectrum altogether. I was hence able to 
determine roughly the shape and dimensions of the prominence. 
It was extremely difficult to fix the exact position of the line at F, although I had 
had no difficulty or even cause for hesitation about the others. It seemed at times to 
lie athwart the F line in the faint spectrum, although at first it had appeared more 
refrangible, especially when it was visible on the solar spectrum itself. 
October 22. — Two days afterwards I had another opportunity of observing the pro- 
minence spectrum, and of endorsing everything I had observed on the former occasion. 
With regard to the F line, I traced the bright line parallel to the dark line and outside 
it (i. e. more refrangible) further than I did on the 20th, but once or twice I caught it 
inside F on the sun. 
I found that a narrow slit was best for D and F, as there are bright bands in the solar 
spectrum at those points. The lines were always visible with the usual width of slit. 
C was bright enough to allow the slit to be widened. 
On this day, as on the 20th, my attention was strongly drawn to certain bright regions 
in the spectrum. 
October 27. — On this date the prominence first observed was no longer on the limb, 
I had to search therefore for a new one ; I found one on the eastern equatorial limb. 
The method of observation previously adopted was changed, and a mixed spectrum of 
the sun’s limb and prominence was obtained. The two spectra were in fact superposed. 
In the case of the line at C, the result was to absolutely eclipse the dark line in the 
spectrum, and to replace it by a vividly bright band (Plate XXXVII. fig. 5). The 
behaviour of the F line was still a puzzle to me. In the spectrum of the light pro- 
ceeding from the exact limb of the sun the bright line was seen more refrangible than 
F, but in the spectrum of the prominence at some distance above the sun the black 
line F was eclipsed (Plate XXXVII. fig. 6). This experiment, which I repeated several 
times, seemed in a measure to explain what I had before observed ; and under this date 
I entered in my note-book : “ It appears that away from the sun’s surface the substance 
gives out less refrangible light than it does when apparently at the surface.” 
November 5. — The next observations were made on this date under superb atmo- 
spheric conditions, and after an important alteration had been made in the instrument, 
enabling me to make the several adjustments with the utmost nicety. 
After the adjustments to the sun’s limb had been made, I at once saw what I imagined 
to be the indication of a small prominence, and swept for a development of it, thinking 
that the portion observed might be one of the loops or lower levels which generally 
separate the higher peaks. Having swept for some distance on both sides the region 
on which the telescope was clamped in the first instance, and finding everywhere the 
same uniformity of height, it at once struck me that I was in presence of something 
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