Constitution of the Sun and Stars, 309 



This produces a region of equatorial calms bordered on either side 

 by zones, in the northern of which south-east trades prevail, and in 

 the southern, north-east. These are succeeded by variable winds 

 in the regions of spots, beyond which the polar current blows over the 

 surface of the photosphere in the form of a north-west trade in the 

 northern hemisphere, and a south-west trade in the southern. In 

 the region of spots, both the polar and equatorial currents make 

 their way to a higher level, and in doing so heave up into a colder 

 situation considerable portions of the upper layer of excessively thin 

 cloud, that which is seen only during eclipses. This, though it may at 

 first take place comparatively gently, will be succeeded by a violent 

 upward motion, because the cloud when raised to a cool region will 

 retain a temperature bordering upon that of the photosphere. When 

 this occurs it will both produce the phenomenon of overhanging clouds 

 seen during eclipses, and give rise to a violent cyclone in the regions 

 beneath, immediately over the photosphere. There is no other part 

 of the sun upon which these conditions prevail : hence the limitation 

 of spots to two bands parallel to the equator. To these results we 

 may assign the probability 2. 



In the next branch of the inquiry we are obliged to have pretty 

 free recourse to speculation ; and the results, though there is much 

 to be said for them, must be received.with the caution which becomes 

 us when we are not at liberty to award a probability higher than 

 1. We are forced to invoke an external agent to account for the 

 periodicity of the spots ; and that which is submitted as apparently 

 the most probable, is a swarm of meteors like those which visit the 

 earth in November every thirty-third year, but extended into a much 

 longer stream. These while they pass through the sun's atmosphere 

 would warm the upper regions above his equator, and thus tend to 

 enfeeble the causes which produce the trade-winds. Hence upon 

 each such visit, the trade-winds, the storms which result from them, 

 and the spots which these occasion would all be moderated. It is 

 remarkable that this hypothesis accounts also for the fact that spots 

 prevail more in one hemisphere than the other, inasmuch as the 

 meteors must act more on one hemisphere than the other, and lessen 

 in it the causes that produce spots, unless we make the highly im- 

 probable supposition that the axis major of the orbit of the meteors 

 lies just along the line in which its plane intersects the plane of the 

 sun's equator. It is also very remarkable that the interval of time in 

 which the spots go through their mutations, which we must of course 

 adopt as the periodic time of the meteors in their orbit, assigns to 

 them an aphelion distance outside and close to the orbit of one of 

 the principal planets, Saturn. There is therefore very considerable 

 ground to suspect that there is such a swarm of meteors which was 

 diverted into the solar system by Saturn * at no very remote 



* The attraction of Jupiter would also have been competent to divert a cluster 

 of meteors into an orbit of the requisite form and dimensions ; but the situation 

 of the orbit would in that case havecaused the meteors to cross the path of Jupiter, 

 so that the planet would have acted ever since as a powerful dispersing agent ; 

 and it does not seem likely that such an influence has been in operation. 



