he remaining one, which is the middle star of the group, is of the
third.

The Greek letters, as borne by the individual stars of the Plough, are a
plain transgression of Bayer's method as above described, for they have
certainly not been allotted here in accordance with the proper order of
brightness. For instance, the third magnitude star, just alluded to as
being in the middle of the group, has been marked with the Greek letter
[d] (Delta); and so is made to take rank _before_ the stars composing
what is called the "handle" of the Plough, which are all of the second
magnitude. Sir William Herschel long ago drew attention to the irregular
manner in which Bayer's system had been applied. It is, indeed, a great
pity that this notation was not originally worked out with greater care
and correctness; for, were it only reliable, it would afford great
assistance to astronomers in judging of what changes in relative
brightness have taken place among the stars.

Though we may speak of using the constellations as a method of finding
our way about the sky, it is, however, to certain marked groupings in
them of the brighter stars that we look for our sign-posts.

Most of the constellations contain a group or so of noticeable stars,
whose accidental arrangement dimly recalls the outline of some familiar
geometrical figure and thus arrests the attention.[30] For instance, in
an almost exact line with the two front stars of the Plough, or
"pointers" as they are called,[31] and at a distance about five times as
far away as the interval between them, there will be found a third star
of the second magnitude. This is known as Polaris, or the Pole Star, for
it very nearly occupies that point of the heaven towards which the north
pole of the earth's axis is _at present_ directed (see Plate XIX., p.
292). Thus during the apparently daily rotation of the heavens, this
star looks always practically stationary. It will, no doubt, be
remembered how Shakespeare has put into the mouth of Julius Caesar these
memorable words:--

"But I am constant as the northern star,
Of whose true-fix'd and resting quality
There is no fellow in the firmament."

[Illustration: PLATE XIX. THE SKY AROUND THE NORTH POLE

We see here the Plough, the Pole Star, Ursa Minor, Auriga, Cassiopeia's
Chair, and Lyra. Also the Circle of Precession, along which the Pole
makes a complete revolution in a period of 25,868 years, and the
Temporary Star discovered by Tycho