518 FIRST REPORT UPON MAGNETIC WORK

now in very favorable positions. Zeta (£)
Ursae Majoris, or Mizar, as it was called
by the ancient Arabians, is the middle
one of the three stars in the tail of the
Great Bear, the small star near it is
Alcor. Delta (<§) Cassiopeiae is at the
bottom of the less perfectly formed Y of
the letter IF, as frequently imagined to
unite roughly the five brightest stars of
this constellation.

The diagram (Fig. 8), drawn to scale,
exhibits the principal stars of the con-
stellations Cassiopeiae and Great Bear,
with Delta (<$) Cassiopeiae, Zeta (£) of
the Great Bear, and Polaris on the
meridian, represented by the straight
line; Polaris being at lower culmination.

In emploj'ing this method the follow-
ing instructions may be followed:

1. Select that one of the two stars,
Delta or Zeta, which at the time of the
year when the observation is made passes
the meridian below Polaris. When the
star passes the meridian above the pole
it is too near the zenith to be of service.
Delta (<$) Cassiopeiae is on the meridian
below Polaris and the pole at midnight
about April 10, and is, therefore, the
proper star to use at that date and for

FIG. 8.—The diagram held perpendicular to the line of sight directed to the pole,
with the right-hand side of the page uppermost, will represent the configuration of
the constellations with Polaris near eastern elongation at midnight about July 11;
inverted, it will show Zeta (C) of the Great Bear and Polaris on the meridian (the
former below and the latter above the pole) at midnight about October 10; and held
with left-hand side uppermost, the diagram will indicate the relative situations for
midnight about January 8, with Polaris near western elongation. The arrows indicate
the direction of apparent motion.