So far as we have yet described our telescope it is optically
complete. If it could be used as a spy-glass by simply holding it
in the hand, and pointing at the object we wish to observe, there
would be little need of any very elaborate support. But if a
telescope, even of the smallest size, is to be used with
regularity, a proper "mounting" is as essential as a good
instrument. Persons unpractised in the use of such instruments are
very apt to underrate the importance of those accessories which
merely enable us to point the telescope. An idea of what is wanted
in the mounting may readily be formed if the reader will try to
look at a star with an ordinary good-sized spy-glass held in the
hand, and then imagine the difficulties he meets with multiplied
by fifty.

The smaller and cheaper telescopes, as commonly sold, are mounted
on a simple little stand, on which the instrument admits of a
horizontal and vertical motion. If one only wants to get a few
glimpses of a celestial object, this mounting will answer his
purpose. But to make anything like a study of a celestial body,
the mounting must be an equatorial one; that is, one of the axes
around which the telescope moves must be inclined so as to point
towards the pole of the heavens, which is near the polar star.
This axis will then make an angle with the horizon equal to the
latitude of the place. The telescope cannot, however, be mounted
directly on this axis, but must be attached to a second one,
itself fastened to this one.

[Illustration with caption: SECTION OF THE PRIMITIVE MOUNTING. P
P. Polar axis, bearing a fork at the upper end A. Declination axis
passing through the fork E. Section of telescope tube C. Weight to