( 591 ) 



2". Willi s(_'\('i-al b'l'aiiiiliorcr lines Iho iiilciisilv or (lie width is 

 i^rcatly d i iii i ii i s li c d. This is dkisI coiispieiKHis with llie 

 broml, dark falcinin bands II and K and with the hydrogen line 

 Hff, these being almost lotally absent in the abnormal spectrnm. 



3". Olher lines, on (he con(raiT, appear u n common lu- 

 stre n g t h e n e d. 



4°. Many lines are more or less displaced. 



The same peculiarities are noticed, though generally in a smaller 

 degree, in the intermedia(e spectrum, so that the latter, in fact, forms 

 a link between the abnormal and the normal spectrum. 



This marvellously complicated disturbance was not confined to 

 light coming from a conijiaratively small part of the solar disk, for 

 instance from the immediate surroundings of a spot; on the contrary, 

 it extended almost eipially over the whole width of the spectrum and 

 w^as tiierefore nearly the same for all the light which came from a 

 \'ery great area of the Sun. 



The moments of the 1 2 exjiosures and the exact date had not been 

 recorded, but there was sufficient evidence that the whole process 

 of the disturbance lasted only a very short time. 



Hale calls the phenomenon : "a remarkable disturbance of the 

 reversing layer". But is it not almost impossible to imagine a rather 

 thin layer in the solar atmosphere undergoing suddeidy and simul- 

 taneously ovev a great part of the sun such a thorough change, as 

 to make its absorbiiig and radiating })ower in some parts of (he 

 spectrum for a while nearly unrecognizable ? 



It occurred to me, therefore, that the origin of (he phenonienon 

 should l)e looked for somewhere on the })ath of (he light between 

 the Sun and the Earth. If on this path there be media, causing 

 anomalous (lisj)ersion, the beam must show an altered composition. 



As 1 formerly indicated ^), the |)roperties of (he chromospheric 

 ligh( may be derived from the sup[)Osilion, (hat (his light has been 

 scat(ei'ed out of the i)hotos|)heric light by anomalous dispersion. 

 According to this hypothesis the spectrum of the chromosphere 

 informs us, which are (he kinds of light, that may follow rather 

 strongly cui-ved paths in (he solar a(mosi)here. So the idea suggested 

 itself, that the same weaves might [)lay a sd-iking jnirt in Hale's 

 abnormal sjiectuuL 



In order to investigate the question as impardally as possible, 1 

 marked (before eonsultiiig IIai.k's (able or a (able of chromosphere 



1) Proc. Roy. Acad. Amst. II, p. .•)7r)-5cS8; III, \>. l',K)-203; IV, p. 16,9-171; 



Plivsikalisclio Zoitsrlifift i, p. I'.)"! ':W. 



40 



Proceedings Royal Acad. Auislerdam. Vul. V. 



