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ing mass of gases in its outer parts to be composed so as to emit 
almost exclusively hydrogen-, calcium-, heliumlight, whilst the radiations 
of sodium, magnesium, titanium, iron are supposed to originate in deeper 
layers, a.s.o.'). We, on the contrary, by the introduction of anomalous 
dispersion are permitted to suggest, that throughout the 
gaseous body, as well inside as outside the critical sphere, 
the various elements are altogether intrinsically mixed 
(granting that in the mixture the quantity of materials with greater 
specific gravity must grow with the depth). For wherever there 
are local differences of density in the mixture, caused by currents, 
whirls ete., the conditions for irregular ray-curving are present, and 
it is evident that specially those elements of the mixture, which 
possess an exceptionnally high dispersing power for certain waves 
of the transmitted light, will be able to reveal their presence even 
at great distances from the disk, while other substances, though 
also present at the same places, remain invisible there. Thus a 
purely optical explanation may be given of the fact, that the different 
gases of the sun are seen separated, even though we suppose them 
to be thoroughly mixed. 
And surely this last supposition is the simpler by far; it even neces- 
sarily follows from the fundamental idea, that the Sun may be considered 
as a rotating, heat-radiating mass of gas, for in such a body the 
constituent parts must continually mix. 
A few months ago the main character of the motion that must go 
on in a sun, supposed to be gaseous, has been discussed by R. EMDEN *). 
He applies to the Sun the same mathematical deductions, which had 
been devised by von HerMmHoLtz for investigating the kind of motion 
which in our terrestrial atmosphere must result from the united 
influence of heating by the Sun and of the daily rotation *). Though 
EmMpEN supposes the gaseous’ Sun to be limited by a well-defined 
surface, and so far accepts the prevailing views on the constitution 
of this celestial body, still his mathematical formulae are absolutely 
independent of the existence of a boundary surface, and so are fully 
applicable to a sun, such as we are considering here. 
Radiation causes the outer layers to cool down soonest; they 
sink inwards and are replaced by ascending hotter gases, so that, 
1) As appears from a paper in the Physik. Zeitschr. 3. S. 259—261: entitled 
,Ueber die Doppellinien im Spectrum der Chromophäre” Scummr adheres to this 
conception, even after having taken into consideration the possibility of explaining 
the light of the chromosphere by anomalous dispersion. 
2) R. Eupen, Beiträge zur Sonnentheorie. Ann. d. Phys. [4] 7, p. 176—197. 
3) H. von Hermnorrtz, Gesammelte Abhandlungen I, p. 146, III p. 287—355. 
