THE SUN. 77 



25 or 30 of north, and not quite so far, or in such 

 abundance in south latitude; W\\\\ d^ compafatiz^e/y s^got- 

 less intermediate belt, of five or six degrees broad be- 

 tween them, answering to our region of equatorial calms. 

 The resemblance is so striking as most strongly to suggest 

 some analogy in the causes of the two pheenomena and 

 it has been suggested that as our trade winds originate in 

 a greater influx of heat from without, on and near the 

 equator, than at the poles, combined with the earth's 

 rotation on its axis : so the maculiferous belts of the sun 

 may owe their origin to a less'^ equatorial ejflux of heat, 

 combined with the axial rotation of that luminary.t 

 There is another extremely remarkable feature in the 

 appearance and disappearance of these spots. I have 

 said that they are not permanent. Sometimes, indeed, 

 but rarely, one and the same spot lasts long enough, after 

 disappearing at the western edge of the sun, to come 

 round again and reappear at the eastern ; and it has 

 happened that a spot has lasted long enough to reappear 

 four or five times ; but for the most part this is not the 

 case. But as regards the number of spots which appear 

 on the sun at different times, there is the greatest pos- 

 sible difference. Sometimes it is quite spotless ; at 

 others the spots swarm upon it : and as many as fifty or 

 sixty spots or groups, large and small, have been seen at 

 once, arranged in two belts. 



{zd.) Now, it has lately been ascertained by a careful 



* Misprinted greater in the original lecture as it appeared in 

 Good Words. 



t " Results of Astronomical Observations at the Cape of Good 

 Hope," by the author, p. 434., 



