523 
ing to Sr. Joun the observed displacements tell against the exist- 
ence of the Einstein effect, whereas Gresik and Bacnem conclude 
from their observations that the gravitational shift is in evidence 
both as regards direction and magnitude. The effect of radial motion 
has been taken into account in these investigations. 
None of the above observers has, however, considered the possibility 
that anomalous dispersion might influence the position of the lines. 
The object of the present investigation is to approach the problem 
from the point of view that Fraunhofer lines are in the main 
dispersion lines’). 
It is realized that this interpretation of the solar spectrum differs 
profoundly from the current notion that one is dealing with a mere 
absorption spectrum ; we are, therefore, justified in accepting it only 
if there are convincing reasons for so doing. 
One of these is for instance the fact thaf the said interpretation 
enables us to establish, without introducing additional hypotheses, 
a comprehensive system of explanations of a great variety of solar 
phenomena which, when explained on the basis of the ordinary 
supposition as to the nature of Fraunhofer lines, lead to several 
difficulties and unsatisfactory conceptions. 
The strongest support, however, for the new interpretation of the 
spectrum is found in certain general properties of the Fraunhofer 
lines, which are readily deduced from the supposition that the lines 
are in the main dispersion lines, but of which, from other points 
of view, no explanation whatever has as yet been offered. Such 
properties are: . 
1. The general displacements of the Fraunhofer lines towards 
the red are very different in magnitude (ranging indeed from 
+ 0,020 A to — 0,007 A), even when comparing lines of one and 
the same element, and bear no relation to the displacements by 
pressure as observed in the laboratory. (Cf. especially the publications 
by EvrrsneD and his collaborators, of the Kodaikanal Observatory). 
1) Attention has first been called to the existence of dispersion bands and 
dispersion lines by one of us in 1904: Proc. Acad. Amsterdam VII, 184, 140, 
323; Astroph. Journ. 21. 271, 278, 286 (1905). Further investigations, on this 
special type of spectral lines are to be found a.o. in these Proc. IX, 848 (1906) ; 
XII, 266 (1909); XIII, 2 (1910); Le Radium 7 (Oct. 1910); these Proc. XIII, 
881, 1263 (1911); The Observatory 37, 252 (1914); Astroph. Journ. 40, 1 (1914); 
43, 43 (1916); Arch. néerl. Serie III A, tome IV, 51, 150 (1917); tome V, 
116 (1918). 
Cf. also the inaugural dissertations by Dr. B. J. van per Praars (Utrecht, 1917, 
also published in Arch. néerl. série II] A, tome V, 132) and by Dr. P. H. van 
Cirrerr (Utrecht, 1919). 
