362 THE CHEMISTRY OF THE SUN. [CHAP. 



prominences, and should not be brightened on passing from the 

 arc to the spark. 



The actual observations of the lines made at Sohag are 

 shown in the accompanying map, and these eclipse observations 

 are compared with the lines thickened in spots, the lines ob- 

 served in the prominences by Tacchini and those intensified on 

 passing from the arc to the spark. The Fraunhofer lines are 

 also given according to Angstrom, and the iron spectrum of 

 the arc and spark according to Angstrom and Thalen the 

 latter corrected. 



The observations during the eclipse were made seven minutes, 

 three minutes, and two minutes before totality, as the air was 

 gradually darkened ; successive veils, as it were, being gradually 

 lifted, as I have explained, so that the more delicate phenomena 

 could be successively seen. 



Dealing with the iron spectrum we begin (seven minutes before 

 totality) with one short and brilliant line constantly seen in 

 prominences, never seen in spots. Next, another line appears, 

 also short and brilliant, constantly seen in prominences. And 

 now, for the first time, a longer and thinner line appears, 

 occasionally noted as widened in spots : while last of all we get 

 very long, very delicate relatively, two lines almost constantly 

 seen widened in spots, and another line not seen in the spark 

 and never yet recorded as widened in the spots. 



The procession from the hot to the colder is apparent, and 

 the simplicity of the spectrum as opposed to the Fraunhofer 

 spectrum even yet, is eloquent of the gradual approximation 

 which would be still possible if the darkness could be greater 

 and our attack more complete. 



It will be noted over what a small range of spectrum the 

 observations extend. We want similar observations over a 

 wider range during future eclipses, and to do this work pro- 

 perly many observers armed with similar instruments must 

 divide the whole or part of the solar spectrum amongst them, 



