90 
b. Limiting case of exclusive dispersion (£ = 0): 
6(0,i) car Sa lel ee RE Packie 
1+oH 1+oH 
Here £ = coefficient of absorption, 6 = coeff. of diffusion, H = height 
of the asmosphere, « and 5 are two numerical constants. 
In his article: “Diffusion und Absorption in der Sonnenatmosphare”’ 
(Sitz. Ber. d. K. Akad. zu Wien, Abh. IIa. Bnd. 125 (1914)). A. 
Devant by the aid of data which he derives from ABsot’s observa- 
tions on the decrease of the intensity of radiation on the sun’s dise 
from the centre towards the limb (Annals of the Astr. Observ. of 
Smithsonian Inst. Vol. III, Washington 1918, p. 158), tries to decide 
which of the two causes, absorption or dispersion, appears to be 
most active on the sun. 
By means of a kind of “trial and error” method he succeeds in 
deriving a formula: 
0.5 Hoos §-+¢—0.0405 sei (0.5 —cos i) 0.3804 -+ 0.3136 cos i 
1+0,0405 A+ ‘ 
which is halfway between (1) and (2) and yields numerically 
accurate values. This seems to point to this that the diffusion effect 
by far preponderates, but is yet influenced by a slight absorption. 
In how far the considerations through which he arrives at for- 
mula (3), are of value, must be left undecided here. It is certain 
that the numerical values are pretty accurate, as table I shows 
convincingly. 
p07) = 
TABLE I. 
A = 0.433 u | A = 0.604 u A=1.031 u 
cost 
.. |6(0,é)| Obser- lib Obser- b (On) Obser- 
BOD | ved | O00) OG vea | 20.0 OUT ved 
value x value x value 
1.0 | 1.2752 | 453 456 0.9486 | 111 111 
0.9 | 1.1906 | 423 419 1.0164 | 381 380 | 0.9175 | 107 107 
0.8 | 1.0996 | 390 384 
0.7 | 1.0006 | 355 348 
0.6 | 0.8932 | 317 309 
0.5 | 0.7764 | 276 2u 
0.4 | 0.6506 | 231 238 
0.3 | 0.5180 | 184 192 
0.8491 | 99.4 100 
0.8137 | 95.2 95.8 
0.7765 | 90.9 90.0 
0.8476 | 318 313 
0.7366 | 86.2 86.2 
0.6912 | 80.9 80.9 
0.6917 | 259 265 
0.5863 | 220 230 
—_ 
° 5 e a 
Dp 
> 
oO 
Co 
© 
© 
ie) 
© 
© 
0.9656 | 361 360 0.8838 | 103 105 
