( 585 ) 
metrically distributed on either side of the corresponding FRAUNHOFER- 
lines; if so, they seem to coincide with the latter ; but in certain places 
of the limb the case must arise that the bright lines would appear 
to have shifted their position with regard to the absorption-lines. 
For in proportion to the distribution of the density of the vapours, 
it will be, in turns, especially the rays with very great refractive index 
(on the red side of the absorption lines) and those with very small 
refractive index (on the violet side of them) that are curved towards us. 
As, upon the whole, the density of the gases of the solar atmosphere 
will decrease rather than otherwise in proportion as they are farther 
from the centre, it may be expected (according to what we observed 
with regard to Fig. 4) that the bright lines will oftener shift their 
position with respect to the FRAUNHOFER lines in the direction of 
greater wavelengths than in that of smaller. 
These details will probably become clearly visible in the eclipse- 
photograms obtained with slit-spectrographs with great dispersion. 
It is not impossible that in many of the chromosphere-lines a dark 
core may be seen. 
Summarising what we have said, we maintain the following position 
with respect to that part of the solar atmosphere situated outside 
what is called the photosphere. 
The various elements whose presence in that atmosphere has been 
inferred from spectral observations, are much more largely diffused 
in it than has generally been assumed from the shape of the light 
phenomena; they may be present everywhere, up to great distances 
outside the photosphere, and yet be visible in few places only; their 
self-radiation contributes relatively little to their visibility (with the 
possible exceptions of helium and coronium) ; the distances, at which 
the characteristic light of those substances is thought to be seen 
beyond the sun’s limb, are mainly determined by their local differ- 
ences of density and their power to call forth anomalous dispersion. 
In conclusion I wish to say a few words concerning phenomena 
presented by the sun-spots. In the spectrum of these spots many of 
the FRAUNHOFER-lines appear considerably broadened (see e. g. the 
diagram in Lockyer, Chemistry of the Sun p. 100). The cause for 
this has been sought in the presence of very dense absorbing gases, 
and the broad bands have been attributed exclusively to absorption. 
The question is whether the second conclusion that we have drawn 
from the phenomena of refraction in a sodium-flame (p. 580) is not 
applicable here. 
We proceed from the opinion that in a sunspot are found great 
