400 
MR. LOUIS VESSOT KING ON THE SCATTERING AND 
atteimatioii of solar ratliatioii and for the intensity. and ijiiality of sky radiation. 
Even at sea-level the effect of “ atmospheric dust ” can be taken into account in a 
simple manner in the formulae for absorption and scattering. Should future observa¬ 
tions support the validity of the simple law expressed liy equation (2) connecting the 
coefficient of attenuation with the wave-length, we may with considerable assurance 
make use of the law to obtain the coefficients for very short or very long wave-lengths 
when the direct method of calculation from high and low sun observations leaves room 
for considerable uncertainty owing to the small Intensities in the solar spectrum at 
these wave-lengths and owing to other experimental difficulties. 
Schuster* points out in this connection the extreme importance of determining 
accurately the form of tlie solar intensity curve outside the earth’s atmosphere for 
short wave-lengths, since the effect of a solar atmosphere in absorbing and scattering 
radiation is to give rise to an intensity-curve whlcli does not agree with that given by 
Planck’s formula especially for short wave-lengths. 
Absorption and scattering of radiation by the sun’s atmosphere, taken in conjunc¬ 
tion with effects of self-illumination, constitutes a problem analogous to that just 
considered for the earth’s atmosphere. By making a comparison between the 
calculated variation of intensity of radiation of different wave-lengths over the solar 
disc and the results of observation it will be possible to determine from the intensity 
curve of the normal solar spectrum outside the earth’s atmosphere the intensity-curve 
at the radiating layer of the sun. This corrected curve may then be compared with 
that given by Planck’s formula and a closer approximation made to the temperature 
of the sun than the values now given. This investigation tlie writer hopes to l)e able 
to deal with in a future communication 
* Schuster, lor. cit. 
