338 THE CHEMISTRY OF THE SUN. [CH. xxiv. 



The ordinary solar spectrum is always included as one 

 of the horizons. Thus in the case of iron all the iron lines were 

 singled out from the Fraunhofer lines and were given sepa- 

 rately, each with its true intensity. 



The diagrams given are small portions of these maps which 

 were all on a large scale prepared for each 100 observations of 

 spots and for each region examined. They will show the method 

 of record and comparison adopted. 



In the horizon at the top marked " Sun," we have the iron 

 lines recorded among the Fraunhofer lines. Below we have 

 the lines given as iron lines by Angstrom, who used an electric 

 arc; while lower down we have the iron lines recorded by 

 Thalen, who used the electric spark. It will be seen that there 

 is a very considerable difference in the spectrum of iron as ob- 

 tained by means of the spark and by means of the arc, and that 

 there is an equal difference between the spectrum of iron in the 

 sun, that is to say, in the total solar absorption registered by the 

 Fraunhofer lines, and the spectrum of either the arc or the 

 spark. It is also to be noted that the solar spectrum is more 

 like the spectrum of the arc than the spectrum of the spark. 



The results in the case of the spots are mapped as follows. We 

 have in the vertical lines a record of the lines which are affected 

 in each spot, and each of the spaces included between the 

 horizontal lines represents the lines most widened in a particular 

 spot, the date being given on the right-hand side. 



Now the wonderful thing that one is at once struck with in 

 all the iron maps alike, is the absolute and complete irregu- 

 larity of the whole result. There is no continuity among any of 

 these lines. A careful inspection of the maps shows us that, 

 speaking in a general way, each of the lines is seen in one spot 

 or another absolutely without the other. We have an inversion 

 in the appearance of the lines when passing from spot to spot. 



Further, whenever we get a line intensified by Thalen, we 

 miss it in the spots, and, as a rule, what happens is that the 



