

xxviii.] CHANGES IN CORONA. 44?, 



(2) In the central plane of the ring over the equator, the 

 particles to be disturbed by the currents will be more numerous ; 

 a rapid descent, therefore, in this central plane will be impos- 

 sible, for the reason that the condensed matter has to fall 

 perhaps a million of miles through strata of increasing tem- 

 perature ; there will, therefore, be no spots. 



The lower corona where the corona is high, and it is highest 

 over the equator, acts as a shield or buffer, volatilisation and 

 dissociation take place at higher levels. Where this occurs, 

 spots are replaced by a gentle rain of fine particles slowly 

 descending; instead of the fall of mighty masses and large 

 quantities of solid and liquid materials, volatilisation will take 

 place gradually during the descent, and at the utmost only a 

 veiled spot will be produced. 



It will be gathered I think then from the above that if 

 such a ring really exists, it may have great influence in deciding 

 the exact latitude for the outbreak of spots and the rate at which 

 the action slows down at the equator. 



16. By the hypothesis, as the falls produce a higher temperature 

 in the lou'er atmosphere ; at and after the maximum the corona will 

 be brighter, and the spectrum will be more truly a gaseous one than 

 at and after the maximum. 



This is in strict accordance with all the observations of the last 

 twenty years. The brightness of the corona at the minimum 

 in 1878 was estimated at i of that of the preceding maximum 

 in the year 1870. The light of the corona was very feeble in 

 1886, three years from the maximum, the preceding maximum 

 having taken place in 1883. Unfortunately I did not see the 

 corona this year, but I saw the stars between the clouds, almost 

 as during the night, certainly more than on a full moon 

 night ; while in 1878 from an elevation of some 7,000 feet in 

 the Rocky Mountains, in the clearest air perhaps in the world, 

 I saw very few. 



