118 OUTLINES OF NATURAL PHILOSOPHY. 



116. The Paths of the spots thus traced, are 

 observed to be rectilineal at two opposite sea- 

 sons of the year, the beginning of June and the 

 beginning of December, and to cut the ecliptic 

 nearly at an angle of 7 20'. Between the first 

 and the second of these seasons, the paths of the 

 spots are convex upward, or to the north, and 

 acquire their greatest curvature about the mid- 

 dle of that period. In the following six months, 

 the paths of the spots are convex toward the 

 south, and go through the same series of changes. 

 They appear to be elliptic arches. 



In the beginning of March and September, when 

 the opening of the elliptic paths is at its maximum, 

 the smaller axis is to the greater as 13 to 100. 

 LA LANDE, Astronomie> 3233. 



117. The preceding appearances may be ex- 

 plained, by supposing the spots to be opaque 

 bodies, attached to the luminous surface of the 

 sun ; the sun having a revolution on an axis 

 inclined at an angle of 7 U 20' to the axis of the 

 ecliptic. 



The apparent revolution of a spot is performed in 27 

 days ; but in this time the spot has done more than 

 complete an entire revolution, having, in addition 

 to it, gone over an arch equal to that which the sun 

 has described in the same time in his orbit. This' 



reduces 



