170 
HAROLD’S DISCUSSIONS. 
fall his apparent course across the skj is along the 
celestial equator. From March 21st the earth moves 
daily toward the southern end of its orbit, which 
makes the sun 
appear to move 
steadily north 
of the celestial 
equator. Thus 
his apparent 
path forms a 
spiral, passing 
through 23.5° 
in ninety days, 
when his ver¬ 
tical rays shine 
upon a circle 
which has been 
called the trop¬ 
ic of Cancer. 
On June 21st 
the earth enters 
its northward course, not exactly toward the pole star, 
but in a plane that makes an angle of 66.5° with the 
line from that star to the earth. Three months later, 
September 21st, it reaches that point in its orbit where 
the sun is again directly over the equator. On De¬ 
cember 21st, when the earth reaches the north limit 
of its orbit, the sun’s vertical rays fall upon the tropic 
of Capricorn, and he appears to us far south. These 
changes in the sun’s course across the sky may easily 
be observed by anyone. 
Fig. 84. —Total eclipse of the sun in 1860. 
The moon passed between the sun and 
the earth. (Feilitzsch.) 
