they appear at 9
o'clock P.M. in mid-season.

To facilitate finding and observing the constellations, the student
should face in the direction indicated in the text. This applies to
all constellations excepting those near the zenith.

The four large plates are so arranged that the observer is supposed to
be looking at the southern skies. By turning the plate about from left
to right, the eastern, northern, and western skies are shown
successively.

On many of the diagrams the position of nebulae is indicated. These are
designated by the initial letter of the astronomer who catalogued
them, preceded by his catalogue number, as for instance 8 M. signifies
nebula number 8 in Messier's catalogue.

The magnitudes assigned to the stars in the diagrams are derived from
the Harvard Photometry. When a star is midway between two magnitudes
the numeral is underlined, thus _2_, indicates a star of magnitude
2.5.

If a star's magnitude is between 1 and 1.5 it is regarded as a
first-magnitude star. If it lies between 1.5 and 2 it is designated
second magnitude.

THE CONSTELLATIONS OF SPRING.

[Illustration: Map showing the principal stars visible from Lat. 40[deg]
N. at 9 o'clock April 1st.]

URSA MAJOR (er'sa m[=a]'-jor)--THE GREAT BEAR. (Face North.)

LOCATION.--Ursa Major is probably the best known of the constellations,
and in this work I presuppose that the reader is familiar with its
position in the heavens. It is one of the most noted and conspicuous
constellations in the northern hemisphere, and is readily and
unmistakably distinguished from all others by means of a remarkable
cluster of seven bright stars in the northern heavens, forming what is
familiarly termed "The Dipper."

The stars [a] and [b] are called the pointers, because they always
point toward the Pole Star, 28-3/4[deg] distant from [a].

Alioth is very nearly opposite Shedir in Cassiopeia, and at an equal
distance from the Pole. The same can be said of Megres, in Ursa Major,
and Caph, in Cassiopeia.

The star [o] is at the tip of the Bear's nose. A clearly defined
semicircle begins at [o] and ends in the pair [i] and [k] at the
extremity of the Bear's right fore paw. This group of stars resembles
a sickle. Note little Alcor close to Mizar. This star was used by the
Arabs as a test of good eyesight.

Mizar and Alcor are known as the horse and his rider.

This plate shows the Bear lying on his back, his feet projected up the
sky;