BROOKLYN BOTANIC GARDEN 
LEAFLETS 
Series IX Brooklyn, N.Y., June 1, 1921. No. 5 
TIME AND SUNDIALS 
On the sundial in the garden. 
The great sun keeps the time: 
A faint, small, moving shadow. 
And we know the worlds are in rhyme. 
But if once that shadow should falter 
By the space of a child’s eyelash. 
The seas would devour the mountains, 
And the stars together crash. 
— R. W. Gilder. 
In the spring of 1920 there was installed in the children's 
garden a sundial, presented by the 1914 graduates of the garden 
teachers’ course, with a shaft presented by the graduates of 1919. 
For centuries before clocks were invented sundials were used. 
The inscription “I count only sunny hours” is often found on 
sundials. When the sun shines, time is indicated by a shadow 
on the dial, marked off to correspond with the hours. 
The essential point about a sundial is that the part throwing 
the shadow, the gnomon, must be parallel to the axis of the 
earth. That is, at any place the gnomon must be at an angle 
equal to the latitude. If the North Pole were really a pole pro- 
jecting above the surface it would make an ideal sundial; that is 
for the half-year during which the sun is there above the horizon. 
At any time the shadow of the pole would point to the part of 
the earth which has midnight, the place under the sun having 
noon, as shown in Fig. 1. 
The simplest form of sundial is one in which the dial face is 
slanting, so as to be perpendicular to the earth’s axis. This 
practically reproduces the North Pole condition at any place. A 
central rod, parallel to the earth’s axis, throws the shadow. 
However, with this form of dial during the six winter months 
the sun would shine on the zinder side, that is during the time 
the sun shines on the south pole. 
In the ordinary horizontal sundial the dial face is parallel to 
the plane of the horizon, or to the surface of still water. It is in 
fact a “ North Pole dial ” projected at an angle. Thus the East 
and West spaces become larger than those near the noon mark. 
Speaking more exactly, North and South lines would be length- 
ened in proportion to the secant of the latitude. In making a 
