overhead. On an autumn evening he is towards the north-west, the length
of the set of seven being somewhat inclined to the horizon. Finally, on
a winter's evening, he is low down towards the north, the length of the
set of seven stars being nearly in a horizontal direction.

Having found the seven stars, we make use of the pointers [alpha] and
[beta] (shown in Plate 1) to indicate the place of the Pole-star, whose
distance from the pointer [alpha] is rather more than three times the
distance of [alpha] from [beta].

Now stand facing the Pole-star. Then all the stars are travelling round
that star _in a direction contrary to that in which the hands of a watch
move_. Thus the stars below the pole are moving _towards the right_,
those above the pole _towards the left_, those to the right of the pole
_upwards_, those to the left of the pole _downwards_.

Next face the south. Then all the stars on our left, that is, towards
the east, are rising slantingly towards the south; those due south are
moving horizontally to the right, that is, towards the west; and those
on our right are passing slantingly downwards towards the west.

It is important to familiarise ourselves with these motions, because it
is through them that objects pass out of the field of view of the
telescope, and by moving the tube in a proper direction we can easily
pick up an object that has thus passed away, whereas if we are not
familiar with the varying motions in different parts of the celestial
sphere, we may fail in the attempt to immediately recover an object, and
waste time in the search for it.

The consideration of the celestial motions shows how advantageous it is,