( 582 ) 
Their typical form appears very strikingly in the hydrogen lines 
of the chromosphere. 
There is no reason to assume that the above considerations, with 
regard to sodium vapour, do not hold good as well for other gases 
and vapours. With some of these the anomalous dispersion has 
been proved already '); with others we have been less successful; 
but the dispersion theories point to its existence in a more or less 
degree in all substances. 
The characteristic form of the chromosphere lines might, of course, 
also be accounted for, as is generally done, by the strongly radiating 
luminous gases and metallic vapours which are thought to be 
present in the chromosphere and of which the density near the 
photosphere must then be taken to be very considerable and to be 
rapidly decreasing at greater distances. The observed light would 
then be emitted by those glowing vapours. 
Our view of the origin of the chromosphere light does not by 
any means preclude the possibility of this light owing its existence, 
partly at least, to self-radiation of incandescent gas; what we have 
shown is, that it may also be refracted photosphere light. Further 
investigation of the various phenomena of the sun must decide 
which explanation goes farthest in considering the whole subject. 
Sometimes the chromosphere lines appear under very singular 
forms, with broadenings, ramifications, plumes, detached parts etc. 
(cf. Lockyer, Le. p. 120). Thus far this has been accounted for 
only on the principle of Dorper, viz. by assuming that the radi- 
ating gases move towards, or away from, us with tremendous 
velocity — even as much as 200 kilometers per second and more. 
Astronomers are all agreed that this explanation is open to many 
objections of which we need not remind the reader here. 
Beside DoppLer’s principle, however, we find in the anomalous 
dispersion another, according to which a gas has the power to 
originate, under certain circumstances, light differing in wavelength 
from the characteristic rays of that substance. 
Let us suppose, for example, that at some distance above the 
sun’s limb there is a quantity of hydrogen, with great varieties of 
density in some of its parts. It will emit not only its own charac- 
teristic light, but will, here and there, also deflect earthwards the 
photosphere light of adjacent wavelengths. This will, of course, 
manifest itself in exerescences or ramifications of the hydrogen lines 
or as isolated light patches in their neighbeurhood. 
1) WINKELMANN, Wied. Ann, 32, p. 439. 
