318 THE CHEMISTRY OF THE SUN. [CHAP. 



In these 200 spots, out of 172 lines of iron which we might 

 have seen only 72 were observed altogether ; out of 120 lines of 

 titanium which we might have seen only 38 were seen ; and 

 then the number goes on decreasing : 24 in the case of nickel, 

 of which 9 were seen ; 19 in the case of zinc, of which 5 were 

 seen; 13 of magnesium, of which 4 were seen; 12 of platinum, 

 of which 1 was seen, and so on. 



The final upshot is, therefore, that at the spot-level we do 

 not see the Fraunhofer spectrum, as we ought to do on the old 

 theory. What we do see is a small percentage of the lines, 

 and we see them under conditions which are entirely 

 unexpected. 



These, though the earlier results, are not the only ones 

 which we may hope to get by going on with the work. At 

 present the dates of the spots have alone been recorded. But 

 this is not enough ; we must know the actual positions of the 

 spots on the sun. We must note whether each particular spot 

 is in the northern hemisphere or in the southern hemisphere, 

 with the view of determining whether there is any chemical 

 difference between the north part of the sun and the south p'art ; 

 and then again we must compare the latitudes of spots, with the 

 view of determining whether there is any difference in the 

 chemistry of the spots according to the latitude. This particular 

 point is just now being worked up, and it really does look as if 

 the sudden changes in the spectra noted from time to time may 

 have been due to the fact that the spots compared were spots 

 varying very considerably in latitude, and it would not surprise 

 me to find that spots which are very like each other in their 

 spectra will be found to be situated more or less in the same 

 degree of latitude, whether the same degree of latitude north 

 or south we do not know. And there is another question, too. 

 I pointed out that there is a considerable number of lines seen 

 in the spectrum of the arc which are left out of the spectrum of 

 the spark. Now, will that help us at all in our inquiries ? I 



