414 Sir Norman Lockyer and I>r. W. .1. S. Luckyer. 



Comparison of Solar and Terrestrial Weather. 



It has long been known that a cycle of solar weather begins in 

 about lat. 32 N. and S., and in a period of eleven years ends in about 

 lat. 5 N. and S. 



Just before one cycle ends another commences. The greatest 

 amount of spotted surface occurs when the solar weather-changes pro- 

 duced in the cycle reach about lat. 16X. and S. 



It becomes, therefore, of the first importance to correlate the times 

 of mean solar temperature, and of the + and - heat pulses, with the 

 solar weather cycle, in order to arrive at the temperature-history of the 

 sun during the period which now concerns us. This may be done as 

 follows : 



Connection of the Spots with Prominences. 



In 1869, when a sunspot maximum was approaching, the promi- 

 nences were classified by one of us into eruptive and nebulous; the 

 former showing many metallic lines, the latter the hydrogen and 

 helium lines chiefly. This conclusion, which was published in 1870, 

 was subsequently confirmed and adopted by Secchi, Zollner, Sporer, 

 Young, and Respighi. 



In the same year prominences on the sun's disc were also observed 

 by one of us by means of the C and F lines.* 



The eruptive prominences, unlike the nebulous ones, were not 

 observed in all heliographic latitudes ; but, according to the extended 

 observations of Tacchini and Kicco, had their maxima in the same 



' Boy. Soc. Proc.,' vol. 17, p. 415. 



