342 





B' 



A" 



-\ h 



1 



isr K-i)'i?' K-i)j? - 



5'^ A' "^ A 



A' 



1 



+k ' + 



/, , (n -l)'i?' (« -1)5- 



+ 





,+|/,+(=.^ + ^'>^- 





I 



i(12) 



In order to estimate the mimerical value of this expression we 

 base ourselves on the result of observations of Fabry and Buisson, 



o 



who found the widening at the limb to be approximately 0,010 A 



o o 



with lines varying from 0,07 to 0,16 A in width (mean width 0,1 J A). 

 The mean width of those othei lines, taken from the observational 

 material of Mount Wilson and Kodaikanal concerning limb-centre 

 displacements, for which the existence of mutual influence has been 



o 



stated ') by us in tiie above mentioned papers, amounts to 0,09 A. 

 Taking these data into consideration, we have calculated the value 



of the expression (12) after substituting 5 = 0,100 A, S'— = 0,010 A, 



and, in succession, — — = ± co . ± 4, ± 1, and 0. The results 



k 



2A 

 have then been plotted as ordinates against abscisses -^ (which, 



therefore, re|)resent distances of the lines expressed in their width 

 as unit). We so obtained the full drawn curves of Fig. 7 (p. 346). 

 They represent (for a refraction line) b}" how many thousandth parts 



o 



of an Angstrom unit the middle point M' h between the boundaries 

 of a limb-line is shifted in excess of the middle point Mb between 

 the boundaries of the corresponding centre-line, in consequence of 

 the presence of an equally strong neighbouring line, if this is situated 

 at a distance equal to 3, 2, 1 times the estimated width of the 

 lines. It will be seen that the repulsion is already perceptible at a 



1) W. H. Juuus, Astroph. Journ. 54, 92, (1921); W. H. Jutius and M. Minnaert, 

 Ann. d. Phys. 71, 50, KAYSER-Festheft, 1923. 



