TRANSACTIONS OF SECTION A. 933 
4, The close agreement of photographs taken at different times during an 
eclipse, and especially between photographs taken during the same eclipse at places 
many hundreds of miles apart. 
Considering the force of gravity on the sun, and the circumstance that comets 
have passed unscathed through the coronal regions, we cannot regard the corona 
as a true solar atmosphere, that is, as a continuous mass of gas held up by its own 
elasticity, which extends several hundred thousand miles above the photosphere. 
Up to a certain point the spectroscope gives to us definite information as to the 
condition of the matter about the sun which forms the corona. We learn that 
there is incandescent solid or liquid matter, which also reflects to us light from 
the photosphere. The spectrum of bright lines, which is relatively fainter and 
varies greatly at different eclipses, tells us of glowing gaseous matter which 
accompanies the solid or liquid matter. As the solid or liquid matter can exist 
in the corona only in the form of discrete particles of extreme minuteness, the 
corona must consist of a fog, in which the particles are incandescent, and in which 
the gaseous matter does not form a continuous atmosphere. 
It has been suggested that the matter of the corona is furnished by meteoroids, 
and by the lost matter of the tails of comets. Though some planetary meteoroids 
may be thrown into the sun, and there are meteoroids which doubtless fall directly 
into the sun from space, yet we can scarcely suppose so steady an inflow of 
meteoroids as would be needed to maintain the corona in the state of permanence 
in which we know it to exist. A similar difficulty presents itself more strongly on 
the view that the corona is fed by the débris of comets’ tails. 
It seems to me much more probable that the matter of the corona is supplied 
by the sun. This view is supported by the spectroscopic evidence, for the coronal 
gas is shown to consist of substances which exist also in the photosphere. The 
structure seen in the corona is much more in harmony with the view that the 
matter is going up from the sun, than that it is coming down upon the sun. 
We have now to consider under what dynamical conditions matter coming 
from the sun can take on forms such as those we see in the corona, and can pass 
easy. to such enormous distances, in opposition to gravitation, which is so powerful 
at the sun. 
There is another celestial phenomenon very unlike the corona at first sight 
which may furnish a clue to the true answer to this question. The head of a large 
comet presents us with luminous streamers, rifts, and curved rays, which are 
not very unlike, on a small scale, some of the appearances which are always 
present in the corona. We do not know for certain the conditions under which 
these cometary phenomena take place, but the only theory upon which they can 
be satisfactorily explained, and which now seems to be on the way to become 
generally accepted, attributes them to electrical disturbances, and especially to a 
repulsive force acting from the sun, probably electrical, which varies as the surface, 
and not like gravity, as the mass. A force of this nature in the case of highly 
attenuated matter can easily master the force of gravity, and as we see in the tails 
of comets, blow away this thin kind of matter to enormous distances in the very 
teeth of gravity.? 
If such a force of repulsion, acting from the sun, is experienced in comets, it 
must also be present near the sun, and may well be expected to show its power 
over the matter ejected from the sun. Such a force would be present if we suppose 
the sun’s surface to possess permanently an electric potential of the same name. 
The sun may acquire such a potential from processes always going on, or if once 
charged, would doubtless remain so, and on this supposition it is not necessary to 
assume local electrical disturbances. But electrical disturbances must be present on 
the sun on a very grand seale in connection with the ceaseless and fearful activity 
of the photosphere. Through these disturbances the ejected matter might come 
1 Proc. Roy. Inst., vol. x. p.9. Also papers by Bredichin in the Annales de T Ob- 
servatoire de Moscou, and Astr. Nachr., No. 2411. Also Stokes, On Light as a Means 
of Investigation, p. 70 et seg. See also papers by Professor Young in the Amer. Jour. 
Science; and by Mr. Proctor in The Sun, 3rd ed., pp. 326-427. 
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