384 POPULAR LECTURES AND ADDRESSES. 



are due to the sun's own substance, and not to 

 external influences of any kind. It is, however, 

 quite possible, and indeed many who know most 

 of the subject think it probable, that some 

 of the chief phenomena due to sunspots arise 

 from influxes of meteoric matter circling round 

 the sun. 



The energy of chemical combination is as nothing 

 compared with the gravitational energy of shrink- 

 age, to which the sun's activity is almost wholly due. 

 A body falling forty-six kilometres to the sun's 

 surface or through the suns atmosphere^ has as 

 much work done on it by gravity, as corresponds 

 to a high estimate of chemical energy in the 

 burning of combustible materials. But chemical 

 combinations and dissociations may, as urged by 

 Lockyer, in his book on the Chemistry of the 

 Sun, just now published, be thoroughly potent 

 determining influences on some of the features of 

 non-uniformity of the brightness in the grand 

 phenomena of sunspots, hydrogen flames, and 

 corona, which make the province of solar physics. 

 But these are questions belonging to a very splendid 



