79 
seen that this cannot be the case, for the radiation at the limb will 
not present such a variety of temperature, irregular refraction, 
‘i / 
Fig. 3. 
diffusion, ete. as that in the centre, because at the limb only radiation 
from a smaller number of layers contributes to the total radiation. 
The radiation at the limb will therefore have an energy curve with 
a maximum which is not so flat as that for the central radiation, 
and which, as we only receive radiation of lower temperature, lies 
somewhat more towards the side of the longer wavelengths (fig. 3 III). 
When we now compare the curves fig. 31, II, and III, it appears 
that in the wavelength-region AB the limb radiation will have a 
relatively stronger, in BC a relatively slighter intensity than would 
be the case if the distribution of the energy were the same as in 
the centre. 
When we now put the central radiation for all the wave-lengths 
= 100, this is graphically represented by a straight line C parallel 
to the wavelength-axis (lig. 4). The limb radiation can then be 
represented by an almost straight line 7, which runs about parallel 
to the wave-length-axis, but which exhibits an oscillation in the 
region ABC. 
These radiations will be weakened by the diffusion and irregular 
refraction in tbe atmosphere outside def (fig. 2), light of the 
shortest wavelengths most. When again we put the resulting central 
