THE SUN'S CORONA AND HIS SPOTS. 7 



was nearer that of maximum than that of minimum disturb- 

 ance. We must pass over Wyberd's observations of the 

 corona in 1652, at least until some direct evidence as to the 

 sun's condition shall have been obtained from the papers or 

 writings of the observers of that year. I note only that 

 Wyberd saw a corona. of very limited extent, having indeed 

 a height not half so great as that of many prominences 

 which have been observed during recent eclipses. If the 

 theory we are examining should be established beyond 

 dispute, we should be led to infer that the year 1652 was 

 in reality a year of minimum solar disturbance. Perhaps 

 by throwing in such a minimum between 1645 an d 1666, 

 with of course a corresponding maximum, the wild irregularity 

 of the sun-spot changes between 1645 an d 1679 would be to 

 some degree diminished. 



We are now approaching times when more satisfactory 

 observations were made upon the corona, and when also we 

 have more complete records of the aspect of the sun's 

 surface. 



In 1706 Plantade and Capies saw a bright ring of white 

 light extending round the eclipsed sun to a distance of 

 about 85,000 miles, but merging into a fainter light, which 

 extended no less than four degrees from the eclipsed sun, 

 fading off insensibly until its light was lost in the obscure 

 background of the sky. This corresponds unmistakably 

 with such a corona as we should expect only to see at a 

 time of many sun-spots, if the theory we are examining is 

 sound. Turning to Wolfs list, we find that the year 1705 is 

 marked as a year of maximum solar disturbance, and the 

 year 1712 as that of the next minimum. Therefore 1706 

 was a year of many sun-spots in fact, 1706 may have been 

 the year of actual maximum disturbance, for it is within the 

 limits of doubt indicated by Wolf. Certainly a corona 

 extending so far as that which Plantade and Capies saw 

 would imply an altogether exceptional degree of solar 

 disturbance, if the theory we are considering is correct. 



In 1715 Halley gave the following description of the 



