230 Original Articles. [ April, 
rotation derived from the paths of the spots across his disc agree on 
the whole satisfactorily, no such good accordance is found between the 
times of rotation so deduced. Galileo concluded from his observations 
(of course rudely) a synodic period of 28 days ; Scheiner, in 1630, of 26 
or 27, corresponding to a sidereal period of 254, or thereabouts ; 
Cassini, 25°59; Lalande, 25°42; Laugier, as a mean result, 25°34; 
Kyseus, 25°09 ; and Boehm, 25°32; the discordance between which is 
too great to be considered satisfactory. Observers, moreover, had 
noticed that, not only different spots gave different results, but that the 
same spot observed in several successive revolutions gave results greatly 
at variance with each other. Thus the observations of M. Laugier 
afforded periods varying from 24°88 to 26°25 days; and Professor 
Fearnley of Christiania, from observations of a very remarkable spot 
in 1857, which presented itself three times on the disc, deduced a 
series. of periods from its passages across and reappearances on the dise, 
of 25°46, 25°67, 25°83, 25-87, and 26°23 days, respectively and succes- 
sively. Such differences are far too great to have arisen from error of 
observation, and can only be attributed to proper motion of the spots 
‘themselves relative to the body of the sun, arising from their floating in 
the solar atmosphere, of which their relative change of heliographical 
situation suffices of itself to indicate the movement. This conclusion 
was drawn by M. Peters, from an elaborate series of observations made 
in 1845-6, in which he first clearly pointed out that the period of 
rotation deduced from such observations is that of the sun’s atmosphere, 
not of its globe, and is affected, for any particular spot, by whatever 
atmospheric drift, permanent or temporary, may subsist in the region 
occupied by it. Thus a way was opened by assiduous observations of 
the spots to a knowledge of the existence and laws (if any) of the solar 
atmospheric currents. About the same time was put forth by the 
author of this notice, a surmise, from the law of distribution of the 
spots in two tropical belts, with an intermediate spotless equatorial 
zone, that their origin might perhaps be sought in regular solar winds, 
analogous in their essential features to our trade-winds, and owing 
their origin to a different rate of emission of heat in the equatorial and 
polar regions, and a consequent difference of temperature in the two 
regions.* On the occasion of the spot-minimum of 1855-6, Mr. Car- 
rington, who from 1858 downwards had been assiduously and sys- 
tematically observing them, was led to make a very important remark 
as to the distribution of the spots in latitude. He found that, as the 
epoch of the minimum drew on, their average heliographical latitude 
decreased; the higher latitudes beyond 20° N. and S. becoming 
deserted, while the equatorial zone became comparatively more and 
more frequented by them; and this went on steadily till the epoch of 
the minimum was attained. After this a sudden and most decided 
change took place. The equator was deserted, and on the reappear- 
ance of the spots their average latitudes, N. and 8., were found to 
exceed 20°, the intermediate zone being now as remarkable for their 
relative paucity as it was before for their relative abundance. On 
* «Results of Cape Observations, 1847.’ 
