Megrez, Alioth, and Mizar (with its comrade) -- are moving with
practically the same speed in an easterly direction, while the other
two, Dubhe and Benetnasch, are simultaneously moving westward, the
motions of Benetnasch being apparently more rapid. The consequence of
these opposed motions is, of course, that the figure of the ``Dipper''
cannot always have existed and will not continue to exist. In the
accompanying diagrams it has been thought interesting to show the
relative positions of these seven stars, as seen from the point which
the earth now occupies, both in the past and in the future. Arrows
attached to the stars in the figure representing the present
appearance of the ``Dipper'' indicate the directions of the motions
and the distances over which they will carry the stars in a period of
about five hundred centuries. The time, no doubt, seems long, but
remember the vast stretch of ages through which the earth has passed,
and then reflect that no reason is apparent why our globe should not
continue to be a scene of animation for ten thousand centuries yet to
come. The fact that the little star Alcor placed so close to Mizar
should accompany the latter in its flight is not surprising, but that
two of the principal stars of the group should be found moving in a
direction directly opposed to that pursued by the other five is
surprising in the highest degree; and it recalls the strange theory of
a double drift affecting all the stars, to which attention was called
in the preceding chapter. It would appear that Benetnasch and Dubhe
belong to one ``current,'' and Merak, Phaed, Megrez, Alioth, and Mizar
to the other. As far as is known, the motion of the seven stars are
not shared by the smaller stars scattered about them, but on the
theory of currents there should be such a community of motion, and
further investigation may reveal it.

From the ``Great Dipper'' we turn to a constellation hardly less