Now, taking a second year after leap year (because the declinations of
that year are about the mean of each set of four years), find the days
of the month when the sun has these different declinations, and place
these dates, or so many of them as can be shown without confusion,
opposite the corresponding marks on FDG. Draw the _sun-line_ at the
top of the card parallel to the line ACB; and, near the extremity, to
the right, draw any small figure intended to form, as it were, a door
of which a b shall be the hinge. Care must be taken that this hinge is
exactly at right angles to the _sun-line_. Make a fine open slit c d
right through the card and extending from the hinge to a short
distance on the door,--the centre line of this slit coinciding
accurately with the _sun-line_. Now, cut the door completely through
the card; except, of course, along the hinge, which, when the card is
thick, should be partly cut through at the back, to facilitate the
opening. Cut the card right through along the line FDG, and pass a
thread carrying a little plummet W and a _very_ small bead P; the bead
having sufficient friction with the thread to retain any position when
acted on only by its own weight, but sliding easily along the thread
when moved by the hand. At the back of the card the thread terminates
in a knot to hinder it from being drawn through; or better, because
giving more friction and a better hold, it passes through the centre
of a small disk of card--a fraction of an inch in diameter--and, by a
knot, is made fast at the back of the disk.

To complete the construction,--with the centres F and G, and radii FA
and GA, draw the two arcs AY and AZ which will limit the hour-lines;
for in an observation the bead will always be found between them. The
forenoon and afternoon hours may then be marked as indicated in the
figure. The dial does not of itself discriminate between forenoon and
afternoon; but extraneous circumstances, as, for instance, whether the
sun is rising or falling, will settle that point, except when close to
noon, where it will always be uncertain.

To _rectify_ the dial (using the old expression, which means to
prepare the dial for an observation),--open the small door, by turning
it about its hinge, till it stands well out in front. Next, set the
thread in the line FG opposite the day of the month, and stretching it
over the point A, slide th