78 THE SUN. 



comparison of all the recorded observations of the spots, 

 that the periods of their scarcity and abundance succeed 

 one another at regular intervals of a trifle more than five 

 years and a half: so that in eleven years and one-tenth, 

 or nine times in a century, the sun passes through all its 

 states of purity and spottiness. Thus, for instance, in 

 the present century, the years 1800, 181 1, 1822, 1833, 

 1844, 1855-6 were years in which the sun exhibited few 

 or no spots, while in the years 1805, 1816, 1827, 1838, 

 1849, i860, the spots have been remarkably abundant 

 and large. Several attempts have been made to connect 

 this with periodical variations in the weather, with hot 

 and cold years wet and dry ones years of good and 

 bad harvests, etc. ; but though I believe there is some 

 such connexion, it is so overlaid and, as it were, masked 

 by the multitude of causes which act to produce what 

 we call the prevalent weather of a season, that nothing 

 satisfactory has been made out. But there are two classes 

 of phccnomena or facts which occur here on earth which 

 certainly do stand in very singular accordance with the 

 appearance and disappearance of the sun's spots. The 

 first is that splendid and beautiful appearance in the sky 

 which we call the Aurora or Northern lights ; and which, 

 by comparison of the recorded displays, have been ascer- 

 tained to be much more frequent in the years when the 

 spots are abundant, and extremely rare in those years 

 when the sun is free from spots. The other is a class of 

 facts not so obvious to common observation, but of very 

 great importance to us ; because it is connected with* the 

 history and theory of the mariner's compass, and with 



