l telescope. It can be
attached by wires to the telescope-tube, and adjusted each night before
commencing observation. The adjustment is thus managed:--a low power
being applied to the telescope, the tube is turned towards a bright
star; this is easily effected with a low power; then the finder is to be
fixed, by means of its wires, in such a position that the star shall be
in the centre of the field of the finder when also in the centre of the
telescope's field. When this has been done, the finder will greatly help
the observations of the evening; since with high powers much time would
be wasted in bringing an object into the field of view of the telescope
without the aid of a finder. Yet more time would be wasted in the case
of an object not visible to the naked eye, but whose position with
reference to several visible stars is known; since, while it is easy to
bring the point required to the centre of the _finder's_ field, in which
the guiding stars are visible, it is very difficult to direct the
_telescope's_ tube on a point of this sort. A card tube with wire
fastenings, such as we have described, may appear a very insignificant
contrivance to the regular observer, with his well-mounted equatorial
and carefully-adjusted finder. But to the first attempts of the amateur
observer it affords no insignificant assistance, as I can aver from my
own experience. Without it--a superior finder being wanting--our
"half-hours" would soon be wasted away in that most wearisome and
annoying of all employments, trying to "pick up" celestial objects.

It behoves me at this point to speak of star-maps. Such maps are of many
different kinds. There are the Observatory maps, in which the places of
thousands of stars are recorded with an amazing accuracy. Our beginner
is not likely to make use of, or to want, such maps as these. Then there
are maps merely intended to give a good general idea of the appearance
of the heavens at different hours and seasons. Plate I. presents four
maps of this sort; but a more complete series of eight maps has been
published by Messrs. Walton and Maberly in an octavo work; and my own
'Constellation-Seasons' give, at the same price, twelve quarto maps (of
four of which those in Plate I. are miniatures), showing the appearance
of the sky at any hour from month to month, or on any night, at
successive intervals of two hours. But maps intermediate in character to
these and to Observatory maps are required by the