( 447 ) 
must be material in \ a much higher degree, than the regular ray- 
curving round Schmidt’s critical spheres. 
So I imagined«the solar atmosphere to be honeycombed with 
irregular density gradients, which may be steeper than the underlying 
general radial gradient. The views I then held appear from the 
following quotation *): 
“The light of the chromosphere and of the flash lines may be 
symmetrically distributed on either side of the corresponding Fraun¬ 
hofer lines; jf 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 according 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 that the bright lines will oftener 
shift their position with respect to the Fraunhofer lifies in the direction 
of greater wave-lengths than in that of smaller. 
These details' will probably become clearly visible in the eclipse 
photograms obtained with slit-spectrographs of great dispersion. It 
is not impossible that in many of the chromosphere-lines a dark 
core may he seen.” 
Hartmann, on the other hand, says: by anomalous dispersion 
V-light cannot possibly appear with any appreciable intensity in the 
chromospheric spectrum. From his argumentation ■)•we must conclude 
that the scheme of radial density variation was present to his mind, 
but that he did not realize the very probable existence of considerable 
gradients in other directions. 
In this matter Hale and Adams seem to share Hartmann’s opinion. 
We, therefore, will once more draw attention to the importance 
of irregular refraction at the sun’s limb, and inquire whether the 
provisional results obtained by Hale and Adams from their photographs 
°f the flash spectrum are really incompatible with the hypothesis, 
that the chromospheric light is mainly a refraction phenomenon. 
Let our starting-point be the surne supposition, which also served 
88 a base in a recently published paper on “regular consequences of 
b Proc. Roy. Acad. Amst II, p. 584-585; Astron Nachr. 153, S. U2 (1900). 
2 ) Hartmann, l. c . 
