loosened and a bit run through it to bore the other. Finally, a
piece of shafting was roughened by rolling it on a file placed in
both bearings and turned with a brace. The bearings were gradually
tightened until perfectly ground.

The declination axis must be perpendicular to both the hour axis
and the line of sight over the pointer. To insure this, a positive
adjustment was provided. The end of the shaft is clamped in a
short block of wood by means of a bearing like the ones described.
One end of the block is hinged to the axis frame, while the other
end is attached by two screws, one drawing them together, the
other holding them apart. The axis is adjusted by turning these
screws. Each shaft, save the one in the pipe, is provided with
this adjustment.

The pointer is of two very thin strips placed at right angles and
tapered slightly at each end. The clamp is attached as shown in
the illustration. The eye piece is a black iron washer supported
on a small strip of wood. The aperture should be 1/4 in., since
the pupil of the eye dilates very much in darkness. The error due
to large aperture is reduced by using a very long pointer which
also makes it possible to focus the eye upon the front sight and
the star simultaneously. The forward sight is a bright brass peg
illuminated by a tiny electric lamp with a reflector to shield the
eye. The pointer arranged in this way is a great improvement over
the hollow tube sometimes used, since it allows an unobstructed
view of the heavens while indicating the exact point in question.

The circles of the instrument are of aluminum, attached to the
shafts by means of wooden clamps. They were nicely graduated by a
home-made dividing engine of very simple construction, and the
figures were engraved with a pantograph. The reading is indicated
by a cut on a small aluminum plate attached to a pointer. The hour
circle is divided into 24 parts and subdivided to every four
minutes. The figures are arranged so that when the instrument is
set up, the number of hours increases while the pointer travels
oppositely to the stars. The declination circle is graduated from
zero to 90 deg. in each direction from two points 180 deg. apart.
It is, adjusted to read zero when the pointer and two axes are
mutually perpendicular as shown in the picture.

To adjust the instrument it is set up on the iron pipe and the
pointer directed to some distant object. All set screws, excepting
those on the decl