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XXIX.— On the Red Prominences seen during Total Eclipses of the Sun. 
Partl. By Witiiam Sway, F.R.S.E. 
(Read April 5, 1852.) 
The red prominences seen during total solar eclipses, are conspicuous rose- 
coloured objects which appear round the dark edge of the moon, as soon as the last 
rays of the sun have disappeared. In preparing my account of the total eclipse of 
the 28th July 1851, it was at first my intention to have stated some hypothetical 
views which I had formed regarding those remarkable objects, and other appear- 
ances | had observed during the total phase of the eclipse. I found, however, that 
the mere description of phenomena extended to so great a length, as to render 
such a course inexpedient; and I have since delayed resuming the subject, in 
order that by comparing a number of other observations with my own, I might 
be enabled, either to confirm or to modify my views. 
The object of the first part of this paper is, To discuss the evidence afforded 
by the observations of the late eclipse to which I have obtained access, as to the 
nature and locality of the red prominences; and, of the second part, To state the 
views which I have been led to form regarding the cause of those singular objects, 
and their probable connexion with other solar phenomena. 
In inquiring into the nature of the red prominences, I shall examine in suc- 
cession different opinions, which have either been formally announced, or are 
likely to be entertained, regarding them, in order to ascertain which of those hypo- 
theses is most accordant with actual observation. The hypotheses I shall discuss 
are the following, namely, 1s¢, That the prominences are optical phenomena, caused 
by the telescope used in viewing the eclipse,—by the unequally heated state of 
the earth’s atmosphere,—or by the action of the moon’s edge on the rays of light ; 
_ and, 2d, That they are material objects, existing in the sun or in the moon. 
I. On the Hypothesis that the Red Prominences are Optical Phenomena. 
“1. On the Visibility of the Red Prominences to the Naked Eye. 
1. It may be supposed that the red prominences are optical phenomena caused 
by the telescope used in viewing the eclipse; but this opinion is at once disproved 
by the fact, that they are visible to the naked eye. At the late eclipse, although 
I was unable to distinguish the /orms of the prominences with the naked eye, 
I had no difficulty in seeing the position of at least one of them, by the strong 
red tinge it imparted to the adjacent portions of the corona. It was also seen by 
Mr Lane, who observed the eclipse along with me. Mr Avie saw the same pro- 
VOL. XX. PART III. 6D 
