94 Transactions. — Miscellaneous. 



sun, so that it can act, by pressui-e, on the immediate atmosphere of the 

 smi ; and, after compression, it can then, by its increased elasticity, be 

 rebounded off again. 



It is important to distinguisli between those parts of the sun's surround- 

 ings which are influenced and carried round by his rotation on his axis, 

 and those other portions above the reach of his diurnal motion. 



If the sun can draw a comet from the confines of the solar system, can 

 he not also drag after him a large mass of atmosphere, even though it be at 

 too great a distance to partake of his rotation ? We know that comets 

 have passed at times very near to the sun ; and what is the difference 

 between the regular return of such a comet — moving in a narrow ellipse, 

 and, therefore, appoximating to a line perpendicular to the solar surface — 

 and a mass of matter, in gaseous and other states, moving to and fro, but 

 exactly perpendicular to the surface ? 



Micrometrical measurements fail to detect any appreciable polar com- 

 pression in the sun's disc ; it is, therefore, probable that the photosphere, 

 or luminous part of the sun, is nearly uniform in thickness or depth. Both 

 the umbra and penumbra of the solar spots are now acknowledged to be 

 below the surface of this photosphere. Now it can scarcely be admitted 

 that solar storms are sufficient alone to account for the periodic formation 

 of spots. Their general figure is more consonant with the idea that their 

 production is assisted by the comparatively thin photosphere being squeezed 

 yet thinner, and pushed away in certain places. 



It appears also to be an established fact that when the spot fi'equency 

 has passed rapidly or slowly from a minimum to the next maximum, it 

 descends with a corresponding (relative) rapidity or slowness to the next 

 minimum. This I think a certain characteristic of oscillations. 



What, however, is the shape of the elastic medium hereby supposed to 

 be in a state of oscillation ? Even if the true atmosphere, or that portion 

 of the sun's surroundings which actually revolves with the sun, is spherical, 

 we can scarcely suppose the other portion to partake of that figure. 



Circumstances appear strongly in favour of the idea of a flattened 

 nebulous mass extending fi'om the sun to the distant planets ; for the 

 planets moving for ages in one direction must flatten and draw out the more 

 distant portions of the sun's atmosphere, and also those portions which we 

 have good reasons for assuming are ejected in solar eruptions with such a 

 velocity as to carry them too far from the sun to enable them to rotate 

 diurnally around him. 



We know how a light body like a comet is perturbed even by a satellite, 

 and we know that the attenuated matter of a comet can generally hold 

 together by gravity ; it is therefore not unreasonable to assume that this 



