of the Atmospheres of the Earth and the Sun. 189 



is what really exists. Assuming the sun's period of rota- 

 tion to be 25-38 days, he has computed the mean daily drift 

 of the spots, in longitude and latitude, to be as follows, the 

 + sign indicating pole-ward motion in latitude and east- 

 ward in longitude, f 



At 50° north — 61' in longitude + 11' in latitude. 

 30 „ - 25 „ +5 „ 



18 „ - 14 „ +1 

 8 „ + 8 „ - 5 



11 south +10 „ - 3 



19 „ -10 „ +1 

 29 „ -21 „ +4 



45 ,, — 85 „ — 2 (uncertain). 



We thus see a regular decrease in eastward motion from 

 the lowest to the highest latitudes in which spots are ob- 

 served, being what I have inferred from the meteoric theory; 

 but the exact opposite of that which is observed in the 

 earth's atmosphere, and which exist in any atmosphere 

 which is acted on, like the earth's, only by greater heat in 

 lower than higher latitudes, combined with the planet's 

 rotation ; for in any such planet the motion of the whole 

 atmosphere must be westward in the equatorial, and east- 

 ward in tlie middle and higher latitudes. 



In order to explain the motion of the spots in latitude, 

 it is necessary for me to assume that they are formed, and 

 float in the lowest stratum of the sun's atmosphere. 



Were the sun's atmosphere acted on only by the mechani- 

 cal force of the in-falling meteors, the centrifugal force would 

 heap up the air at^the equator, and barometric pressure 

 would be greatest there ; and this excess of pressure would 

 produce currents from the equator to the poles at the sur- 



Carrington's facts, whicli I quote, are most valuable ; but I confess I do not 

 understand the reasoning by which he tries to account for them. 



t It is true that the absolute motions in longitude assigned by Mr Car- 

 rington are quite untrustworthy, as the true period of the sun's rotation is 

 not yet determined. But what we have to do with is the differences in the 

 motions at different latitudes. If it is true that the sun's atmosphere is im- 

 pelled round his body, it follows that the rotation of his body must be slower 

 than has been inferred from observations of the spots. Mr Oarrington thinks, 

 on the contrary, that it is more rapid than he has assumed, in order to con- 

 struct the table. 



NEW SERIES. VOL. XIX. NO. II. APRIL 1864. 2 B 



