44 



Mr. G. J. Stoney on the Physical 



[Recess, 



upward tendency expends itself in somewhat retarding the descending 

 current, but a few degrees on either side, where this obstacle has become 

 sufficiently feeble, it determines extensive upheavals of the lower strata 



Polar calms and 

 ascending currents. 



Zone of variable winds produced by descending currents. 



Southern zone of variable winds produced by currents about to ascend. 



WW 



Northern zone of variable winds produced by cm-rents about to ascend. 



Zone of variable winds produced by descending currents 



Polar calms and ascending 

 currents. 



Diagram of the winds supposed to blow over the photosphere of the sun. 

 of the outer atmosphere, which, however gently they may begin, we 

 have seen will terminate in a cyclone. Hence the two belts of spots 

 on either side of the equator. In somewhat higher latitudes, the equa- 

 torial current having ascended, and, as it were, split the polar current 

 into two sheets, has diverted one of them along the surface of the 

 photosphere. In these regions, therefore, there is a constant wind 

 blowing over the photosphere from the north-west in the northern 

 hemisphere, and from the south-west in the southern. Accordingly, in 

 the two zones of spots there are probably variable winds blowing over the 

 photosphere, the polar and equatorial currents threading their way through 

 each other, and both tending upwards, like the fingers of the two hands 

 interlaced into one another. Meanwhile the equatorial current which had 

 risen into the middle of the atmosphere over the zone of spots exchanges, 

 in the northern hemisphere, its north-westerly direction, first for one due 

 north, and then for one towards the north-east, as it ascends still higher. 



