140 
HAROLD’S DISCUSSIONS. 
was seen in the constellation of Libra, or Leo, as 
the case may be. 
All persons have an interest in the starry heavens, 
especially young people. After a beginning has been 
made, many an hour may be spent in profitable study 
and recreation as well as amusement. 
To start with, it will be helpful to imagine the 
heavens to be a large hollow sphere with the earth in 
the center. The ancients believed that it was really 
so, and thought the stars were tacked on it on the in¬ 
side. This conception is, of course, not a true one. 
Further, imagine the earth turning on its axis in the 
center of the supposed celestial sj^hgre. As we turn 
about, the stars seem to move from east to west, as 
the sun does in the daytime. 
l^ow let us become familiar with a few terms 
used in astronomy. Suppose you are standing on a 
hill, or, better, on the deck of a vessel out of sight of 
land. Directly above your head is the zenith, and in 
the opposite direction through the earth is the nadir. 
The circle all around you, where earth and sky seem 
to meet, is the horizon—that is, the sensible horizon. 
The true or celestial horizon is parallel to this and lies 
in the plane which passes through the center of the 
earth beneath our feet. It cuts the celestial sphere 
into two equal hemispheres. The sensible and the 
real horizon, however, are one and the same in the 
infinite distance of the sky. 
When we speak of the meridian, we mean an im¬ 
aginary great circle which passes from the north star 
through our zenith to the south pole. It divides the 
