August 29, 1878] 



NATURE 



461 



of gas, such as has appeared hitherto, and at another 

 time this might be absent, which seems to be the case at 

 present. 



He further adds that if such changes go on indefinitely 

 it may not be irrational to inquire whether they may not 

 in future produce such extraordinary climatic conditions 

 in the earth as geology teaches us hare existed in the 

 ages of the past. 



Prof. Young was careful not to commit himself to any 

 decided connection between solar and terrestrial climatic 

 changes ; he, however, certainly concurs with me that the 

 corona is fainter and the gaseous elements far less con- 

 spicuous than that observed at previous eclipses, and 

 acknowledges that the different condition of the corona 

 proves a change in the condition of the sun, as the corona 

 acts with it in a sort of sympathy. Dr. Draper is reso- 

 lute on the other side. He is reported to have said : — 



" It is rather sincrular while the sun has been in such a 



quiescent condition for more than two years, that we 

 have not seen more changes in the climate of the earth. 

 This would seem to show that the abnormal condition of 

 the sun at the maximum period of sun-spots, which 

 occurs every eleven years, counts for but little against 

 the total amount of heat that is sent out from the sun at 

 all times. The present observations go to show that the 

 activity or quiescence of the sun makes no perceptible dif- 

 ference in the earth's condition. I do not regard this 

 most marked change in the corona as portending any 

 change in the condition of either climate or crops." 



Finally, on this whole question, I may remark that 

 I have been not a little astonished to find how slowly 

 European work percolates among the men of science 

 here. I have met with few who are familiar with Mel- 

 drum's admirable work, and the discussion to which 

 it has given rise. Still it is a great thing that at all 

 events the cycle of solar changes has forced itself so 

 markedly upon public attention. 



For myself, as I have ever regarded sun-spots as 



KlG. O. 



down-rushes — a term to which I still adhere — I am well 

 content to see this view indorsed by such a chain of facts 

 as the corona has now supplied. In spot-maximum years 

 we have violent up -rushes of gas from the sun's interior, 

 and the corona is mainly built up of such gas. Further, 

 we hare spots, and, if these are not evidences of the 

 return convection currents, we have none other. In 

 spot-minimum years, such as the present, we have no 

 up-rushes, and the corona contains no gas, and there are 

 no spots. Spots, then, are only observed when we have 

 a right to look for the return of the upward current, about 

 which there is no doubt, and the rate of which we have 

 measured. 



But if this puts beyond all question, as I hold it does, 

 the nature of spots, on the other hand, the separation 

 of the gaseous from the continuous spectrum of the 

 corona indicates that we have yet much to learn of the 

 temperature and nature of the corona when the spots are 

 absent. 



So much, then, touching the progress of solar matters 

 during the eclipse of 1878. I have not yet, however, 

 done with the observations. 



There is little doubt, I think, that an intra-Mercuria 

 planet has been found by Prof. Watson. If it will fit one 

 of Lererrier's orbits, and should turn out to be Vulcaiv 

 no doubt astronomers will be able to keep a firm grasp 

 upon it, and sooner or later its elements will be deter- 

 mined. 



Prof. Watson, of Ann Arbor, whose belt, as the 

 papers here put it, is graced with the scalps of I 

 know not how many minor planets, broke off work 

 on a planet beyond Neptune to come to discover 

 one inside Mercury. He went with me in Mr. 

 Silvis' railway photographic car from Rawlins to Sepa- 

 ration on the morning of the eclipse, intending to 

 observe with me at the station we were determined to 

 occupy, with our light equipments, as the number of 

 detached clouds visible at the time of totality on the pre- 



