THE SUN'S CORONA AND HIS SPOTS. 15 



favouring the theory with which we started. Whether any 

 other theory of association between the corona and the sun- 

 spots will better accord with the evidence hitherto collected 

 remains to be seen. 



Turn we now to the eclipse of 1851, occurring nearly 

 midway between the epochs of maximum solar disturbance 

 (1848) and minimum solar disturbance (1856). I take the 

 account given by Airy, our Government astronomer, as he 

 was one of the observers of the eclipse of 1842. 



' The corona was far broader,' he says, * than that which 

 I saw in 1842. Roughly speaking, the breadth was little 

 less than the moon's diameter, but its outline was very 

 irregular. I did not notice any beams project ng from it which 

 deserved notice as much more conspicuous than the others ; 

 but the whole was beamy, radiated in structure, and termi- 

 nated though very indefinitely in a way which reminded 

 me of the ornament frequently placed round a mariner's 

 compass. Its colour was white, or resembling that of 

 Venus. I saw no flickering or unsteadiness of light. It was 

 not separated from the moon by any interval, nor had it 

 any annular structure. It looked like a radiated luminous 

 cloud behind the moon.' 



The corona thus described belongs to that which our 

 theory associates with the period of maximum rather than 

 of minimum solar disturbance. Definite peculiarities of 

 structure seem to have been more numerous and better 

 marked than in 1842. It accords with our theory that 1851 

 was a year of greater solar disturbance than was observed in 

 1842, as the following numbers show: 



Days of Days without New groups 

 observation spots observed 



1842 . . . 307 64 68 

 1851 . . . 308 o 141 



i860 . . . 332 O 211 



I have included the year 1860, as we now proceed to con- 

 sider the corona then seen by Airy. The year 1860 did not 

 belonged to the next period, the time of actual minimum occurring early 



in 1844. 



