470 MR WILLIAM SWAN ON THE 
radiated structure seems therefore to indicate the existence of something tending 
to limit the transmission of the rays to directions normal to the sun’s surface, 
and capable of absorbing them more powerfully at certain points than at others. 
The bright beams of light in the corona strongly resembled sunbeams shining 
through narrow apertures in clouds; and it was indeed that resemblance which 
first led me to entertain the idea that an envelope of cloudy matter surrounds the 
sun. Immediately after witnessing the late eclipse, when I reflected on the strik- 
ing want of continuity I had observed in the illumination of the corona, I was 
strongly impressed with the conviction that something existed near the surface of 
the sun which intercepted his light more at certain points than at others. It then 
occurred to me, that as the red prominences, from their power of reflecting light, 
must also absorb it, the medium which absorbed the sun’s light irregularly, and 
caused the unequal illumination of the corona, might be no other than the matter 
composing the red prominences; that matter being supposed to constitute an 
envelope surrounding the sun, of which the red prominences are only the higher, 
and probably the rarer portions. 
If the faculee are apertures in the envelope of cloud, as has been supposed, it 
will follow that faculz near the sun’s limb may be connected with the bright 
beams in the corona. If, then, a considerable portion of the sun’s surface near 
his limb were intersected by numerous branching faculee, with openings gradually 
increasing in width towards the centre of the group, we should probably have a 
mass of light in the corona like that represented in Plate XII., which was seen at 
the late eclipse about 30° to the east of the sun’s vertex. On the other hand, 
light proceeding from a single long facula in the sun’s limb, presented to the 
eye endwise, might occasion the appearance of the narrow bright beams which 
were seen in the corona; and a considerable variety of effects might be produced 
by faculee whose positions were differently inclined to the visual direction. 
The following queries embody the hypothesis which I have now ventured to 
propose regarding the red prominences, and the other solar phenomena which I 
have supposed to be connected with them :— 
1. May not the sun’s luminous atmosphere be surrounded by an envelope of 
cloud capable of absorbing part of his light, and having the property of appearing 
red when seen by reflected light ? 
2. As the spots on the sun have been supposed to be formed by upward cur- 
‘rents in his atmosphere, may not the same, or similar currents, force up portions 
of the envelope of cloud, and sometimes actually rupture it? 
3. May not the higher portions of the envelope of cloud be seen projecting 
beyond the moon’s limb during the total phase of a solar eclipse, and thus consti- 
tute the red prominences ? 
4. May not this envelope be the chief agent in causing the diminished bright- 
ness of the sun’s disc towards his edges, owing to the greater thickness of the 
ee ee a 
