Upon Sun-Dials and How to Make Dhem 
huge gnomons of dials laid out upon the 
level ground. In modern dialling conven¬ 
ience of construction and of working is, 
however, the next consideration in the selec¬ 
tion of materials; and it has brought stone 
and bronze into the most frequent use. 
That metal is the best suited for the stile or 
gnomon because the slender proportions 
required can best be sustained by it. 
The object of the gnomon is merely to 
supply an edge exposed to the sun at a certain 
angle with the ground. Figure I shows the 
method of laying it out. First: A horizon¬ 
tal base line AB is drawn. With a protractor 
the angle of the gnomon’s face is laid off 
equal to the latitude of the given place the 
dial is to serve. Assuming the instrument 
were to be made for use in New York City 
this angle would be 40° 44" (nearly), the 
latitude of the metropolis. From the point B 
this angle is described until it intersects C—a 
variable distance corresponding to the size of 
the gnomon desired. F'rom C, a vertical 
line is carried to the base-line and the triangle 
thus formed gives the gnomon in its simplest 
form, and would be ready for use save for 
slight modifications we shall mention here¬ 
after. Since only the lower and upper edges 
are needed,—the former for fastening upon 
the dial-face and the latter to receive the 
sun’s rays,—the back of the gnomon may be 
cut away at pleasure or the center may be 
pierced as freely as a draughtsman’s triangle. 
In fact the variety and beauty of the shapes 
so obtained constitute one of the most inter¬ 
esting features of the dials of all periods. 
The angle ABC, Figure I, then, is the 
correct one for the latitude we have selected. 
The next step is to lay out the face of the 
dial. T his is shown in Figure II. 
Draw a horizontal line CD, and at 
its center erect a vertical. From 
the intersection E, as a center, 
describe a circle the radius of which 
will equal the length of the line BC 
in Figure I (the length of the 
gnomon’s face). The points C and 
D upon the circle will be the six 
o’clock points made by the daily 
passage of the sun. Inside of this 
circle another circle should then be 
drawn whose radius should equal 
the length of the line AB in Figure 
I (the base of the gnomon). The 
two quadrants of the outside circle 
A to D and A to C next divide 
into six equal parts—indicated by 
o, o, o, etc. Do likewise with half 
of the inner circle and obtain the 
points z, z, z, etc. From each of 
the points o, o, o, etc., draw lines 
parallel to CD, and from each of 
the points z, z, z, etc., draw lines 
parallel to AE. Mark the points 
of intersection x, x, x, etc., and draw lines 
through them from the central point E. 
Where these lines cross the circles will be 
the hour points. In drawing the figures for 
the hours they should have the same inclina¬ 
tion as the lines radiating from E. The half 
and quarter hours should be made in the 
same way by dividing the distance between 
the points on the outer and inner circle, and 
where the lines from E intersect will give 
the position for the half hours and quarter 
hours. T he minutes, if one chooses to put 
them in can be spaced off with the eye, as 
the distances to be divided are short. The 
lower half of the dial can be laid out in 
precisely the same manner given above and 
the hour marks extended to, say, four o’clock 
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