616 
are found in these different ways, are not equal. It is. therefore, 
necessary when indicating the effective temperature of the sun, 
to state clearly beforehand from what condition imposed on the 
temperature of the absolutely black body which we think as taking 
the sun’s place, it has been determined. 
In what follows the condition has been chosen that the distribution 
of energy in the spectrum of the black body, calculated according 
to the law of PrANCK, will agree as closely as possible with that 
in the sun’s spectrum, as has been derived by ApBor from bolograms. 
Accordingly, the temperature which we should have to assign to 
such a “black sun”, if this condition is to be fulfilled, is the effective 
femperature, which will be discussed in this article, and which, we 
have found, appears to be dependent on the chosen A. 
The relation between 7’ and 2 is once more given below in 
table 1. 
TABLE I. 
Ay A2 T 
0.4 m 0.5 (6400) 
0.5 0.6 9000 
0.6 0.7 10.000 
0.7 0.8 9600 
0.8 1.0 8000 
1.0 1.2 5500 
1.2 1.5 3800 
1.5 1.8 ~ (5400) 
1.8 2.0 — 
The way in which the values of 7’ have been calculated is 
briefly as follows, 
From Puanck’s formula: 
7,211. 10° 
JS 2,1562 X 2890 Ik adt) 
il 
nail te AU 
is obtained for any value of 7, and with any choice of the units 
(factor f), a definite curve Z, =p (2), which represents the distri- 
bution of intensity in the spectrum of the absolutely black body. 
