356 



Mr. J. N. Lockyer. On the 



[May 6, 



Fig. 2. Minimum. 



Tracing of Newcomb's observation of 1878, the brighter portion of corona being 

 hidden by a screen. Shows the equatorial extension and concentric atmo- 

 spheres. 



1871, and also in drawings made before that time, the drawings being 

 read in the light afforded by these photographs. 



I find that the working hypothesis at once suggests to us that the 

 sun-spot period is a direct effect of the atmospheric circulation, and 

 that the latitudes at which the spots commence to form at the mini- 

 mum, which they occupy chiefly at the maximum, and at which they 

 die out at the end of one period in one hemisphere, probably at the 

 moment they commence to form a second one in the other (as happened 

 in 1878 — 9), are a direct result of the local heating produced by the 

 fall of matter from above descending to the photosphere, and perhaps 

 piercing it. The results of this piercing are, the liberation of heat 

 from below, and various explosive effects due to increase of volume, 

 which, acting along the line of least resistance, give, as a return 

 current, incandescent vapours ascending at a rate which may be 

 taken as a maximum at 250 miles a second, a velocity sufficient to 

 carry them to very considerable heights. 



