70 The Total Solar Echipse of 1900. 
corona is well shown, although, of course, the finest details are lost, and there 
is less extension than on the negative. The larger prominences are more clearly 
seen on Plate vu. Both plates exhibit ‘“Baily’s beads’—the bright, isolated 
points of returning sunlight appearing as dark dots in the reversed portion 
of the photograph. 
Miscellaneous Remarks. 
The day of our arrival at Plasencia was much overcast, and the weather had 
been uncertain for some time previously. Subsequently the sky was almost 
absolutely free from clouds, and the transparency at night was very unusual to 
us, accustomed to the hazy skies of our climate. The day of the eclipse was not 
quite so perfect as those preceding, and a few clouds were visible on the horizon. 
The first signal of the immediate approach of totality was caused by the fading 
of a white cloud-bank, which lay in the track of the shadow, owing to the dimi- 
nution of contrast with the darker sky above. The shadow itself was invisible 
both at commencement and close of totality. The position of our station was 
singularly favourable for witnessing the changes of colour in the sky and over 
the landscape, and the effects were marvellously beautiful. During totality 
colours were clearly discernible, and the light must have very considerably ex- 
ceeded that of the full Moon. The view from the hill of Berrocalillo is very 
extensive, the chief features being the picturesque little town of Plasencia towards 
the east, and the snowy summits of the Sierra de Gredos on the north-east ; but 
during totality the light was quite sufficient to distinguish most of the details. 
II. 
Mr. W. E. Witson’s Report. 
The point which I wished to determine was whether it would be possible, by 
suitably coloured screens, to find how far the real corona extends from the Sun, 
and how much of what we see is due to the atmospheric glare. Part of the light 
of the true corona seems to be monochromatic, giving one bright line in the green 
at 1474. If therefore a suitable screen could be found that would cut off all the 
spectrum except that particular ray, we ought to get a true photograph of the 
corona, so far as it is composed of coronium. 
Experiments were made in my laboratory on different screens, and finally 
one was fixed upon which cut off the entire ultra-violet end of the spectrum up 
to the edge of the green. It was made by taking an ordinary cut celluloid film, 
81 by 63, and clearing it in the hypo-bath. After being then well washed with 
