420 THE CHEMISTRY OF THE SUN. [CHAP. 



the zone in which such spots (see page 409 et seq.) appear is 

 limited and is liable to change : these conditions therefore 

 should hold with the metallic prominences. 



Again, what are the facts, always_remembering that the spot 

 appears first in point of time ? 



The Italian observers have not only very carefully observed 

 the prominences from day to day, but they have observed spots 

 and the other phenomena which require continuous investigation. 

 The foregoing diagram puts together in a very convenient 

 form much information which we want in this place. The 

 information extends over three years, so that we have not merely 

 to depend on the result of one year's observation. The curves 

 have a very simple explanation. In the middle of each yearly 

 series E stands for the equator, and right and left of that we 

 have vertical lines giving every 10 of latitude from the equator 

 to the poles south or north for each year. The height of the 

 curves from the base-line represents the number either of spots, 

 faculse, metallic or quiet prominences, seen each year. The spots 

 in the year 1881 had their maximum in latitude 20 N., and 

 12 S. There were no spots either north or south of latitude 

 40, and there were very few spots indeed near the equator of 

 the sun. In 1882 the conditions are a little changed. There 

 are some spots near the equator, and the maximum of spots now 

 is 18 N., and there are more spots this year than there were last, 

 because the curve is higher. Going on to 1883 the maximum 

 of spots has changed from the north of the equator to the south, 

 and in latitude 15 S. we have a reduced maximum, whereas in 

 the northern hemisphere we get very nearly the same quantity 

 in latitude 10 and 20. 



The other curves may now be compared with these, and the 

 point of enormous importance is this, that the maximum of the 

 faculse and of the metallic prominences agree absolutely in 

 position with that of the spots. When one phenomenon changes 

 its position on the sun the other does so also. 



