xxiv.] GENERAL STATEMENTS. 345 



1873, he saw two lines of wave-lengths, 4943 and 5031, about 

 which absolutely nothing whatever is known ; so that it really 

 is, I think, a perfectly justifiable suggestion that these lines are 

 the spectrum of a substance which exists in the chromosphere, 

 which is produced at a much higher temperature than that 

 needed to give us those other forms of " iron " which produce 

 the lines in the spots. 



That is a suggestion which is obvious from a reference to the 

 maps, and if it is correct we must acknowledge that when the 

 sun was in that intense state of quiescence that there were 

 no violent descents nothing to bring cooler vapours from the 

 higher regions of the sun down to obstruct the general tenour 

 of the solar way in the flame region, that at last, in consequence 

 of this wonderful tranquillity, even the iron lines brightened in 

 prominences the only two lines which indicated the presence 

 of iron in them faded away as the iron lines faded from the 

 spots, because iron, whether as we know it or not, faded away. 

 There is no other explanation that I know of. In addition to 

 those two lines we have two other lines about which we know 

 nothing, except that they are probably due to a temperature 

 which we cannot approach. 



We are now in a position to sum up the spectroscopic evidence 

 touching the relation between the spots and prominences. This 

 may be included in the following : 



General Statements regarding Si^ots and Prominences. 



1. The chromospheric and prominence spectrum of any one 

 substance, except in the case of hydrogen, is unlike the ordinary 

 spectrum of the substance. For instance, we get two lines of 

 iron out of 460. Thus we see that the spectrum of a sub- 

 stance in the prominences is very unlike its spectrum out of 

 a prominence, that is, in our laboratories. 



