96 Transactions. — Miscellaneous. 



only from the equatorial side, but also from the polar sides, by the gradual 

 back rush of photosphere. This would prevent the formation of spots in 

 those parts. 



Moreover, as the equatorial parts of the photosj)here become gradually 

 forced into a latitude having a slower motion of rotation, a certain gyratory 

 commotion must ensue tending to break its continuity. These breaks would 

 also, from this reason, be more likely to occur at the beginning of the cycle 

 in the higher latitudes, where there would be greater difference in the 

 comparative speed of the parallels. 



The third difficulty, namely, the acceleration of their rotation in pro- 

 portion to their vicinity to the equator, may be explained under the 

 assumption of the flattened nebulous mass before alluded to, when we con- 

 sider that all the parts of the sun's atmosphere, which rotate with him, 

 must tend to travel at greater velocities the higher they are above the sun's 

 surface. When, therefore, the higher parts, directly over the sun's equator, 

 are caused to descend to the sun's surface, by either a general or local 

 oscillation, they must travel faster than the sun's equator, and act like a 

 constant wind blowing in the direction of the sun's motion. The same 

 result will ha^open, though in a gradually reduced degree, as we depart from 

 the equator ; the solar spots will therefore travel at greater speed the nearer 

 they are to the equatorial regions. After the downward oscillation is termi- 

 nated, the upward one commences ; but by this time the solar spots have 

 mostly disappeared for the photosphere resumes its ordinary thickness. 



This variation in the speed of different parallels of the photosphere, 

 arising from the downward oscillation, must, I think, produce those agita- 

 tions in the photosphere so apparent just before the appearance of spots, 

 and most likely conspires to their formation. The general drift of the spots 

 in lines of parallel, together with the common arrangement of a number of 

 spots in lines parallel to the equator, appear hereby explained. 



The very fact of the solar spots being proved, by observation, to travel 

 faster m the equatorial parts, appears to prove the existence of a lenticular- 

 shaped mass surrounding the sim ; for a merely spherical atmosphere 

 could not, by its downward oscillation, effect a change in their rotation. 



Eegarding the fourth difficulty, of the greater prevalence and size of sun- 

 spots in northern latitudes, it is pretty certain that, owing to the intense 

 heat of the sun's mass, a certain amount of adjustment must be already 

 attained in its photosphere. If then gravity, at the sun's surface, is 

 balanced by the expansive force of heat, any slight alteration in the pressure 

 of his atmosphere must modify the equihbrium of all other forces there 

 exerted. Can it be that the sun's own proper motion in space, in imping- 

 ing on the interstellar medium, gives an additional pressure upon the sun's 



