THE SUN'S CORONA AND HIS SPOTS. 3 



shown that so far as the special sun-spot period from the 

 minimum of 1867 to the minimum of 1878 is concerned, 

 there has been a certain correspondence between the aspect 

 of the corona and the state of the sun's surface, with regard 

 to spots. To assume from that single correspondence that 

 the corona and the sun-spots are related in the same way, 

 would be hazardous in the extreme. We may indeed find, 

 when we consider other matters, that the probability of a 

 general relation of this sort existing is so great antecedently, 

 that but slight direct evidence would be required to establish 

 the existence of the relation. But it must be remembered 

 that before the eclipse of 1878 was observed, with the special 

 result I have noticed, few were bold enough to assert the 

 probable existence of any such relationship ; and certainly 

 no one asserted that the probability was very strong. I 

 believe, indeed, that no one spoke more definitely in favour 

 of the theory that the corona probably sympathises with the 

 sun-spots than I did myself before the recent eclipse ; but 

 certainly I should not then have been willing to say that I 

 considered the evidence very strong. 



We must then look for evidence of a more satisfactory 

 kind. 



Now, although during the two centuries preceding the 

 invention of the spectroscope and the initiation of the solar 

 physical researches now in progress, observations of eclipses 

 were not very carefully conducted, yet we have some records 

 of the appearance of the corona on different occasions, 

 which, combined with the known law of sun-spot periodicity, 

 may enable us to generalise more safely than we could from 

 observations during the present spot-period, though these 

 observations have been far more exact than the older ones, 

 I propose to examine some of these. Necessarily I must 

 make some selection. I need hardly say that even if there 

 were no such relation as that which seems to be indicated 

 by recent observations, and if my purpose were simply to 

 prove, either that such a relation exists or that it does not, I 

 could very readily bring before the reader of these pages 



B 2 



