THE SUN AND SOLAE PHENOMENA. 
305 
It will be seen that the various phenomena of spots, whether 
dark or brilliant, and all the different changes in their form and 
motion and number, are not mere objects of idle curiosity, but 
intimately connected with the economy of our own globe. Should 
the persevering observer merely count the number of spots which 
he remarks pn the solar surface in the course of a year, he would 
confer a boon on science. If, in addition, he accurately deter- 
mines their positions by Mr. Carrington’s plan, the series of 
observations would be extremely valuable. That eminent 
observer has discovered a law of storms in the sun’s atmo- 
sphere, there being a daily drift of the spots in longitude 
which reveals a general equatorial current of thirty degrees 
in breadth in the direction of rotation, whilst a reverse current 
of nearly the same breadth is perceptible beyond it in each 
hemisphere. We are indebted to M. Schwabe for a systematic 
reckoning of the number of spots visible since 1826. In 1828 
the number of groups was 225, which gradually diminished to 
33 in 1833. In 1837 they had increased to 333; and in 1843 
they had fallen to 34. By 1818 the number had again in- 
creased to 330 ; whilst in 1856 only 34 were visible. In 1860 
they had increased to 210 ; and in the years 1861 and 1862 will, 
doubtless, be greater. It must be remembered that all these 
changes are gradual. The periodicity is mi deniable, and may 
be reckoned at about eleven years, though it does not appear to 
be constant, sometimes amounting to nearly fifteen years (as 
the minima of 1784 and 1799), sometimes being only 8-| years 
(as the minima of 1689 and 1698). The observer will per- 
ceive, too, that the zones of disturbance are different year 
by year : sometimes the spots are confined wholly to the 
sun’s equator ; at other times wholly north, sometimes alto- 
gether south of the equator. They seldom pass beyond forty 
degrees of latitude. That they are intimately connected with 
the rotation of the sun on its axis there can be no doubt, but 
that it is solely due to this cause is impossible. There must 
be external atmosphere or internal agitation to cause those im- 
mense ruptures (one of which was measured at 3,780 millions 
of square miles in area) which precedes the effect produced by 
rotation. The amateur astronomer will see what a rich field is 
minute. At the Cape of Good Hope, under a vertical sun, only one inch of 
ice would melt in 2h. 12m. 4-2s. It may be added that according to the 
theory of Mr. Watherston, the debris and fragments of broken material which 
would fall and batter into the sun would (if of the density of granite), cover 
the surface to a depth of twelve miles annually, whilst according to the 
hypothesis of Professor Thomson, a thickness of twenty-four miles would 
fall into it, from the matter of the Zodiacal light coming in contact with its 
photosphere. 
