that semicircle which contains the lowest point (apparently) of the
field is the _northern_ half, the other is the _southern_ half. Over the
oval space just mentioned the reverse holds.

Thus the field is divided into four quadrants, and these are termed
_north following_ (_n.f._) and _south following_ (_s.f._); _north
preceding_ (_n.p._), and _south preceding_ (_s.p._). The student can
have no difficulty in interpreting these terms, since he knows which is
the following and which the preceding _semicircle_, which the northern
and which the southern. In the figures of plates 3 and 5, the letters
_n.f._, _n.p._, &c., are affixed to the proper quadrants. It is to be
remembered that the quadrants thus indicated are measured either way
from the point and feather of the diametral arrows.

Next, of the apparent annual motion of the stars. This takes place in
exactly the same manner as the daily motion. If we view the sky at eight
o'clock on any day, and again at the same hour one month later, we shall
find that at the latter observation (as compared with the former) the
heavens appear to have rotated by the _twelfth part_ of a complete
circumference, and the appearance presented is precisely the same as we
should have observed had we waited for two hours (the _twelfth part_ of
a day) on the day of the first observation.

* * * * *

Our survey of the heavens is supposed to be commenced during the first
quarter of the year, at ten o'clock on the 20th of January, or at nine
on the 5th of February, or at eight on the 19th of February, or at seven
on the 6th of March, or at hours intermediate to these on intermediate
days.