56 



SCENERY OF THE HEAVENS. 



luminary independent of other bodies for these elements, and distributing them to a train 

 of tributaries. It can only be said that activity is a general characteristic of the universe, 

 that rotatory motion seems to be one of the universal laws of nature, and prevails beyond 

 the bounds of our system, the most probable cause of the phenomena of the variable stars. 

 The solar spots are of all shapes and dimensions. The motion of rotation causes their 

 appearance to alter to the eye. A spot seen directly in the middle of the disk is speedily 



impaired as our view of it becomes oblique, 

 and narrows into a line as it is carried 

 towards the western limb. It appears 

 also a mere point at the eastern extre- 

 mity, and gradually opens as the central 

 regions are approached. The apparent 

 direction of the paths described by the 

 spots upon the solar surface is perpetually varying. 

 About the beginning of December they appear 

 to pass in straight lines, as in the figure, in the 

 direction A a. Soon after this period these lines 

 begin to be inflected towards the north, and at the 

 commencement of March they assume the form of 

 the curves represented. The curvature afterwards 

 diminishes, and at the beginning of June they ap- 

 pear again as straight lines, but with an inclina- 

 tion precisely contrary to what it was six months 

 before. After this they begin to be inflected down- 

 wards, taking the form of a curve at the commence- 

 ment of September, with its convex side turned towards the south pole of the sun. By 

 the beginning of December they have exactly the same direction and inclination as at the 

 antecedent twelvemonth. These appearances are invariable year after year. They occur 

 in the same order, and belong to all the spots that have been perceived upon the solar 

 disk. They arise simply from the uniform rotation of the sun upon an axis inclined to 

 the plane of the earth's orbit. Let a common terrestrial globe be taken to represent the 

 sun, with the pole inclined about seven degrees from the zenith, and the wooden horizon 

 placed horizontally in the same plane with the eye of a spectator. If the spectator then 

 walks round the globe, keeping his eye in the plane of the horizon, the circles of latitude 

 will appear in his different positions, straight lines, concave and then convex curves, and 

 thus exhibit the phenomena of the varying yet orderly directions in which the spots seem 

 to traverse the solar surface. 



Intervals of some length have occurred during which . the disk of the sun has been 

 comparatively pure. This was the case from the year 1650 to 1670, and in 1724 he 

 likewise appeared unblemished. But from 1611 to 1629, according to Scheiner, he was 

 never free from tarnish, except for a few days in December 1624. At a more recent 

 date, scarcely a year has passed without spots being seen, many of which have been of 

 great magnitude. Herschel mentions one, the diameter of which exceeded fifty thousand 



