^ 598 ) 



Wc miglit be templed to think of absorption in the corona; for 

 if it be ti'ue that a streanioi- was tni-ned towardt^ the Eartii, the i-ays 

 liad to go an nnconimoidv h)ng wav thi-ough an ai)sorl)ijig nicMUnni. 

 But on closer examination this idea is less prol)abie. 



The particles of the extremely rarefied corona gases will hardly 

 influence each other; their periods will, therefore, be ahnosi absolutely 

 constant, so as to cause very sharp, narrow absorjtlion lines. Tims it 

 is difficult to understand, how an alisorption line, already })resent 

 in the normal solar spectrum, might be strengthened by the absorbing- 

 power of the corona. Further, in studying Halk's table, we observe 

 that many lines Avliich are strong in the abnormal s}>ectrum, show 

 a much smallei- intensity in the intermediate spectrum (taken only 

 a few moments later); whilst the reverse happens as well. \i/.. that 

 lines are strong in the intermediate and very weak in the abnormal 

 spectrum. This hardly tits in with the absorption hypothesis. Some 

 lines showing this [)eculiarity are given in table 111. 



TABLE 111. 

 lines wliose intensity is very dillerent in the intermediate and the abnormal spcdnnii. 



In the chromosphere spectrum corresi)onding lines seem to be 

 wanting. (At l 3905.66 and ). 4057.39 the faint chromosphere line 

 may possibly belong to auolher element than the abuoi-mally streng- 

 thened absorption line). 



To arrive at a more satisfactory explanation of the strengthening- 

 phenomenon we suppose that these absorption lines do indeed cause 

 lujomalous dispersion of neighbouring waves, but in a very slight 



