525 
The complete data on which this conclusion is based will be 
published shortly. At present we only give a summary of the in- 
vestigation, because the result tends to show the necessity of admit- 
ting, when looking for evidence as to the Emsrein effect, that in the 
solar spectrum we are substantially dealing with dispersion lines. 
Adequate material for inquiring into the possible influence of 
neighbouring lines is to be found in W. S. Abas’ measurements 
of the displacements of 467 lines in the spectrum of the sun’s limb 
as compared with the spectrum of the centre of the disk.’) But for 
two or three exceptions these lines are, in the limb spectrum, shifted 
towards the red with respect to their positions in the centre spectrum. 
That in this phenomenon gravitation potential should play any 
perceptible part, is of course excluded. Evrrsuep has convincingly 
shown that these displacements can neither be due to pressure, 
whilst his alternative explanation based on the Doppler principle, 
requiring a specific repulsive force exerted by the earth on the solar 
gases’), appears inacceptable. There is, therefore, sufficient cause to 
seek another explanation of this class of line-shifts. We connect 
these displacements with our hypothesis that Fraunhofer lines are 
in the main dispersion bands, which, indeed, envelop the real ab- 
sorption lines (which are extremely narrow) in a generally asym- 
metrical way. 
If this interpretation is correct, the above mutual influence of 
neighbouring lines must appear, for the shape of the dispersion curve 
in the environment of an absorption line is modified by the presence 
of another absorption line. How that modification must influence 
the degree of asymmetry of the dispersion line has been explained 
in Astrophysical Journal 48, 50—53 (1916). 
In order to select from Apbams’ list those lines for which, from 
the point of view of the dispersion theory, an excess or a deficiency 
of displacement towards the red is to be expected, we proceed as 
follows. 
The columns A and A' of his table are covered with strips of 
„paper, so that the choice cannot be influenced by a knowledge of 
the observed displacements; then the environing region of each line 
of the table is inspected on the atlases of Row.anp and Hraes, in 
order to ascertain whether the line may be presumed to have an 
“effective” companion. Cases in which on either side of the line a 
nearly equally effective companion is suspected, are of course omitted, 
as the opposite influences would neutralize each other wholly or for 
1) W. S. Apaus, Astroph. Journ. 31, 30 (1910); Mt. Wilson Contrib. NO. 43. 
4) EversHED, Kodaikanal Bull. 39. 
34 
Proceedings Royal Acad. Amsterdam. Vol. XXIII. 
