quite common in ancient times before
clocks and watches were invented. At the present time they are
used more as an ornamentation than as a means of measuring time,
although they are quite accurate if properly constructed. There
are several different designs of sundials, but the most common,
and the one we shall describe in this article, is the horizontal
dial. It consists of a flat circular table, placed firmly on a
solid pedestal and having a triangular plate of metal, Fig. 1,
called the gnomon, rising from its center and inclined toward the
meridian line of the dial at an angle equal to the latitude of the
place where the dial is to be used. The shadow of the edge of the
triangular plate moves around the northern part of the dial from
morning to afternoon, and thus supplies a rough measurement of the
hour of the day.

The style or gnomon, as it always equals the latitude of the
place, can be laid out as follows: Draw a line AB, Fig. 1, 5 in.
long and at the one end erect a perpendicular BC, the height of
which is taken from table No. 1. It may be necessary to
interpolate for a given latitude, as for example, lat. 41
degrees-30'. From table No. 1 lat. 42 degrees is 4.5 in. and for
lat. 40 degrees, the next smallest, it is 4.2 in. Their difference
is .3 in. for 2 degrees, and for 1 degrees it would be .15 in. For
30' it would be 1/2 of 1 degrees or .075 in. All added to the
lesser or 40 degrees, we have 4.2+.15+.075 in.= 4.42 in. as the
height of the line BC for lat. 41 degrees-30'. If you have a table
of natural functions, the height of the line BC, or the style, is
the base (5 in. in this case) times the tangent of the degree of
latitude. Draw the line AD, and the angle BAD is the correct angle
for the style for the given

[Illustration: Details of Dial]

TABLE No. 1.

Height of stile in inches for a 5in. base, for various latitudes

Latitude Height Latitude Height
25 2.33 42 4.50
26 2.44 44 4.83
27 2.55 46 5.18
28 2.66 48 5.55
30 2.89 50 5.96
32 3.12 52 6.40
34 3.37 54 6.88
36 3.63 56 7.41
38 3.91 58 8.00
40 4.20 60 8.66

latitude. Its thickness, if of metal, may be conveniently from
1/8 to 1/4 in. ; or if of stone, an inch or two, or more, according
to the size of the dial. Usually for neatness of appearance