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temperatures determined according to PLANcK, are nothing but 
calculated quantities to which a physical sense can hardly be attached, 
and which certainly do not give an insight into the actual tempera- 
tures of the sun. 
If we possessed a means to consider exclusively light that reaches 
us from this photospheric scale, then, according to our supposition, 
every photosphere would possess its own energy spectrum, which 
would vary from photosphere to photosphere, and this for two 
reasons : 
1. The real temperature in the inner layers is different from 
that in the outer. 
2. The radiation, reaching us from the inner layers has under- 
gone a greater loss through absorption and scattering (and, so far 
as the latter cause is concerned, to a much greater degree for the 
shorter wave-lengths than for the longer), in consequence of which, 
even if the real temperature of the different layers were the 
same everywhere, the observed energy spectrum would still be 
different in the different layers. 
What we do observe, however, is not the spectrum modified by 
scattering etc. of every layer separately, but the combination of all 
these spectra together. 
To try and derive an effective temperature from this spectrum, 
which is far from “black” seems to be absolutely unpermissible ; 
because the fundamental condition itself, that the energy spectrum 
used would in its main points resemble that of an absolutely 
black body, has not been fulfilled. 
If, however, we do apply this procedure, it is not surprising 
that the found values of 7 appear in a high degree, to be dependent 
on A, 
The latter may be shown more clearly by the following method. 
Let us imagine an energy spectrum formed by the superposition 
of only two spectra, originating from two really ‘black’ bodies, 
which contribute about an equal amount to the total radiation, 
but whose temperatures differ greatly. Such a case is represented 
in figure 1. 
Let the curve 1 correspond to the absolute temperature 3000°, 
the curve II to 1500°. Then the maxima lie respectively at@A=1u 
and 2 == 2u. Summation of these yields the curve III, but by halving 
the ordinates curve IV has been derived from this, whose area is 
again equal to the area of each of the component curves, i.e. we 
reduce all the cases to equal total radiation. 
It is now easy to see that when we derive the temperature from 
