Manchester Memoirs, Vol. I. (1906), No. T. 21 



after some years distracted from this controversy by the 

 work of the spectroscope, but within the last year our 

 interest has been reawakened in it by some very successful 

 photographs* taken by Mr. Hansky, of St. Petersburg, 

 who has not only photographed these granules, but 

 demonstrated their continuous existence as separate bodies 

 of some kind, moving about among one another. But to 

 identify them as individuals it is necessary to take photo- 

 graphs at intervals of less than one minute, for the move- 

 ments even in a few seconds are large. By measuring 

 the photographs, Mr. Hansky estimates that the velocities 

 of the granules are something like 10 to 20 miles per 

 second. If we may assume that there are in a vertical 

 direction velocities similar to these horizontal ones, we 

 get just the sort of velocity which would suit the pheno- 

 mena of the corona on the lines above indicated. I do 

 not lay, however, too much stress on this illustration, if 

 only for the reason that Mr. Hansky's discovery is too 

 recent. But I would add one word further of what may 

 be frankly called speculation in the direction of very low 

 velocities. 



If for any reason it were to seem probable that veloci- 

 ties even smaller than these might play a part in the 

 phenomenon of the corona, velocities, let us say, of one 

 mile per second, then we must not forget to take into 

 account the possible effect of the sun's rotation. Sup- 

 posing, for a moment, that the particles owed their ejec- 

 tion to this rotation alone, we can see that they would be 

 chiefly flung off from the equator and the corona would 

 have the appearance of a comparatively flat extension, 

 which we see at a time of minimum sunspots. The 

 extension in other directions seen when sunspots are 

 numerous might then be due to the introduction of some 



*Mitt. der Nikolai-Hauptstermvai te zu Pitl/cowo, vol. i, no. 6. 



