THE ECLIPSE OF LAST DECEMBER. 
145 
work of far greater difficulty, and immensely more important. 
More important, because no one could gravely question tbe fact 
that the prominences exist within an atmosphere, while the 
inference that that atmosphere was mainly hydrogenous seemed 
altogether probable, whereas the existence of the dark lines in 
the continuous spectrum of the prominences throws an altogether 
new light on a theory which had long been disputed. 
Whence do these dark lines come ? They cannot belong to 
the inherent light of the corona, nor can they be due to 
absorptive action exerted by the outer parts of the corona on 
the white light producing the continuous background of the 
spectrum. Those dark lines which would be the most marked 
in this latter case, are precisely the lines which appear bright 
in the coronal spectrum — 4he lines of hydrogen. Moreover, it 
is incredible that the cool vapour of sodium exists in quantities 
adequate to account for the presence of the sodium double D 
line ; so that even though no other dark lines were discernible, 
it would be certain that we have not a phenomenon of coronal 
absorption to deal with. No other theory remains, then, than 
this — that the portion of the coronal light which supplies the 
faint continuous spectrum crossed by dark lines is reflected 
sunlight. But how reflected ? Not by matter in the earth’s 
atmosphere, or between the moon and earth, for that is physi- 
cally impossible, apart from the independent evidence just 
obtained against the glare theories. Not by gaseous matter 
near the sun, for Professor Tyndall has proved that matter in 
the gaseous state is incapable of reflecting any light whatever. 
How, then, can this light be reflected, save from that cosmical 
matter independent of the sun, to which Janssen refers, and 
which, as he truly remarks, must exist in his neighbourhood ? 
It seems to me that this discovery of Janssen’s of itself suffices 
to demonstrate the meteoric theory of the origin of at least a 
considerable portion of the coronal light. I have always re- 
garded this theory as irresistibly strong, altogether apart from 
spectroscopic evidence — as strong enough in any case to resist 
the negative evidence based on the failure of spectroscopists to 
recognise the solar dark lines in the coronal spectrum. Now 
that the dark lines have been seen, the basis of the meteoric 
theory, already strong, has acquired double width and firmness. 
of hydrogen above u even the prominences ” by Professor Young’s method 
(that is, by the use of a simple train of prisms), is in direct contradiction to 
his own account of his observations by this method, in which he distinctly 
mentions two minutes as the apparent extension of the four circular images. 
By the old method — which, however, Mr. Lockyer himself denounced last 
year as untrustworthy — he obtained the hydrogen lines at a greater height 
from the sun than this. 
VOL. XI. — NO. XLIII. L 
