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How To Make a Sundial
Lesson CCXXXIII
Method—The diagram for the dial is a lesson in
mechanical drawing. Each pupil should construct a
gnomon (nomon) of cardboard, and should make a drawing
of the face of the dial upon paper. Then the sundial
may be constructed by the help of the more skillful in
the class. It should be made and set up by the pupils.
A sundial in the school grounds may be made a center of
interest and an object of beauty as well.
A sundial made by pupils.

Materials—For the gnomon a piece of
board a half inch thick and six inches
square is required. It should be given
several coats of white paint so that it will
not warp. For the dial, take a board
about 14 inches square and an inch or more thick. The
lower edge may be bevelled if desired. This should be
given three coats of white paint, so that it will not
warp and check.
The gnomon.

To make the gnomon—The word gnomon is from a Greek word
meaning "one who knows." It is the hand of the sundial,
which throws its shadow on the face of the dial,
indicating the hour. Take a piece of board six inches
square, and be very sure its angles are right angles.
Let s, t, u, v represent the four angles; draw on it
a quarter of a circle from s to u with a radius equal
to the line vs. Then with a cardboard protractor,
costing fifteen cents, or by working it out without any
help except knowing that a right angle is 90°, draw
the line vw making the angle at x the same as the
degree of latitude where the sundial is to be placed.
At Ithaca the latitude is 42° 27' and the angle at x
measures 42° 27'. Then the board should be cut off at
the line vw, and later the edge sw may be cut in some
ornamental pattern.
To make the dial—Take the painted board 14 inches
square and find its exact center, y. Draw on it with a
pencil the line A A" a foot long and onefourth inch at
the left of the center. Then draw the line B B" exactly
parallel to the line A A" and onefourth inch to the right
of it. These lines should be onehalf inch apart—which
is just the thickness of the gnomon. If the gnomon were
only onefourth inch thick, then these lines should be
onefourth inch apart, etc.
With a compass, or a pencil fastened to a string, draw
the halfcircle A A' A" with a radius of six inches
with the point C for its center. Draw a similar
halfcircle B B' B" opposite with C' for its center.
Then draw the halfcircle from D, D', D", from c with a
radius of five and threequarter inches. Then draw
similarly from c' the halfcircle E, E', E". Then draw
from c the halfcircle F, F', F" with a radius of five
inches and a similar halfcircle G, G', G" from c' as a
center.
Find the points M, M' just six inches from the points
F, G; draw the line J, K through M, M' exactly at right
angles to the line A, A'. This will
mark the six o'clock point so the figures VI may be
placed on it in the space between the two inner
circles. The noon mark XII should be placed as
indicated (the "X" at D, F, the "II" at E, G). With
black paint outline all the semicircles and figures.
The face of the sundial.

To set up the sundial—Fasten the base of the gnomon by
screws or brads to the dial with the point s of the
gnomon at F, G, and the point v of the gnomon at M, M',
so that the point W is up in the air. Set the dial on
some perfectly level standard with the line A, A"
extending exactly north and south. If no compass is
available, wait until noon and set the dial so that the
shadow from W will fall exactly between the points A,
B, and this will mean that the dial is set exactly
right. Then with a good watch note the points on the
arc E, K', on which the shadow falls at one, two,
three, four, and five o'clock: and in the morning the
points on the arc J' D on which the shadow falls at
seven, eight, nine, ten and eleven o'clock. Draw lines
from M to these points, and lines from M' to the points
on the arc E K'. Then place the figures on the dial as
indicated in the spaces between the two inner circles.
The space between the two outer circles may be marked
with lines indicating the half and quarter hours. The
figures should be outlined in pencil and then painted
with black paint, or carved in the wood and then
painted.
