190 Mr Joseph John Murphy on the Circulation 



face of the sun, where the centrifugal force would be dimi- 

 nished by friction ; just as we have seen that a similar 

 cause produces currents in the earth's atmosphere from Lat. 

 30° to the poles. 



But this is not what we observe. Mr Carrington's table 

 shows that if lines are drawn round the sun at about Lat. 

 15° north and south, the currents in which the spots drift, 

 flow on the polar side of those lines towards the poles, and 

 on the equatorial side towards the equator. We may infer 

 that a parallel of latitude from which currents flow on both 

 sides must be a place of barometric maximum. In the 

 earth's atmosphere, as we have seen, there are two such 

 barometric maxima, but they are at Lat. 28°, about 13° 

 nearer the pole than those of the sun; and in the earth's 

 atmosphere they nearly coincide with the boundaries be- 

 tween the westward trade-winds and the eastward counter- 

 trades. It is, I think, safe to assume that such coincidence 

 must take place in the sun's atmosphere as well as in the 

 earth's ; for there must be an outflow of air at the surface 

 of the earth from both sides of a zone of barometric maxi- 

 mum ; and the effect of the planet's rotation on a wdnd flow- 

 ing to a different latitude, will be to give an eastward direc- 

 tion to one towards the pole, and a westward direction to- 

 wards the equator. I have shown that were the east and 

 west component of the velocity everywhere the same, the 

 boundary of the east and west wind regions would be at Lat. 

 20° 19' 20", in order to have no effect on the planet's rota- 

 tion. But I have further shown, that the force of the east- 

 ward winds of the higher latitudes, must of necessity be 

 greater than the force of the westward winds of the lower 

 latitudes ; so that in order to effect the above-mentioned 

 compensation, the boundary must be on the polar side of 

 the parallel of 20° 19' 20", and with it, if I am right, the 

 zone of barometric maximum.* But in the sun, as we see, 

 that zone is on the equatorial side of 20° 19' 28'''. 



If my reasonings are correct, were the sun's atmosphere 

 acted on only by the meteors, the barometiic maximum 



* The frictional force of a wind is a function of its yelocity and the nature 

 of the surface it passes over ; but we have reason to believe that the sun's 

 surface is everywhere alike, being everywhere liquid from the intense heat. 



