( 583°) 
This phenomenon may be expected especially, when the slit is 
adjusted for the examination of prominences, where violent distur- 
bances take place and where, consequently, considerable differences 
of density occur. 
Though the present explanation of these irregularities in the spec- 
trum is based, like the other one, on the hypothesis that violent 
disturbances in the solar atmosphere go hand in hand with them, yet 
the tremendous velocities, required when applying DoPPLER’s principle, 
dv by no means follow from it. 
A portion, therefore, of all the light that reaches us from chro- 
mosphere and prominences may be due to self luminosity of the 
gases to be found there; but another, and to all likelihood a very 
considerable, portion is refracted photosphere light, reaching us ina 
manner that reminds us of T6PLER’s well-known “Schliecrenmethode’’. 
But there’s this difference, that in the “Schlierenmethode” every 
kind of rays emitted by the source helps to bring out the same 
irregularities of the medium by ordinary refraction; as a rule no 
colour-phenomena are to be seen, the dispersion of most media being 
small compared with the average deviation of rays. The chromo- 
sphere gases, on the other hand, are to be seen in characteristic 
colours, because they have an exceptionally high or low refraction 
index for particular sorts of light. In this case the dispersion is 
great in comparison with the average deviation of the rays. 
Momentarily disregarding the self-radiation of the gases in the 
solar atmosphere we shall — if the slit is radially adjusted — find 
those chromosphere-lines to be longest and brightest which show 
the greatest anomalous dispersion. We have seen that the two 
sodium-lines show considerable difference in their respective powers 
to call forth this phenomenon. Let us make the pretty safe suppo- 
sition that also the different hydrogen-lines and the other chromo- 
sphere lines show analogous individual differences, and we have the 
explanation why in the chromosphere spectrum some lines of an 
element are long and others short, and why the relative intensity 
of the lines of an element is so different in this spectrum from that 
in the emission spectrum or in the FRAUNHOFER absorption spectrum. 
A careful examination of the anomalous dispersion of a great number 
of substances will, of course, have to be made before it can be made 
out in how far our view will account for the facts already known 
or yet to be revealed in the chromosphere spectrum. Amongst 
other things it must then appear whether those elements whose lines 
