200 MO VEMENTS OF THE SPHERE. 



of the disc of the full moon. Ah, what exquisite iris colours ! 

 They mark the meeting-points of the bright with the obscured 

 hemisphere : a circular line carried through all these points 

 would exactly separate day and night. On the one side, 

 motion and life and glow; on the other, silence and shade 

 and calm. This line moves, carrying with it in its movement 

 day and night, the illuminated and the darkened hemisphere ; 

 it moves from east to west, so that the bright hemisphere and 

 the shadowy one, whose union forms what may be called the 

 photo-adumbrated sphere, revolves, in four-and-twenty hours, 

 round an axis which coincides at this moment the 2ist day 

 of March, according to the " terrestrial worms," with the axis 

 of the earth rotating on itself in an inverse direction, that is 

 to say, from west to east. Let us note this coincidence : it 

 is remarkable ; inasmuch as, at the equinoxes, the terrestrial 

 equator divides exactly the illuminated and the obscured 

 hemisphere into two equal parts, one of which is situated to 

 the north, the other to the south, and their line of separation 

 coincides with a meridian circle. 



But I see another, and much slower movement, very clearly 

 defined. The axis of rotation of the photo-adumbrated sphere 

 does not remain parallel with the terrestrial axis of rotation j 

 it retires from it little by little, so as to form with it an angle 

 which attains its maximum at the summer solstice (21-22 June); 

 afterwards, returning upon itself, it coincides anew with the 

 terrestrial axis of rotation (the autumn equinox), to make an 

 angle in the contrary direction, whose maximum, of the same 



