0 a device used outside, especially in the past, that consists of a thin piece of metal attached to a flat surface printed with numbers. It shows the time by the metal making a shadow on the surface as the sun moves across the sky.
1 a device that uses the light of the sun to show the time of day
As the Sun moved in the sky, the dark shadow on the sundial showed the change of time.
Of course, sundials didn’t work when there was no sun – at night or on a cloudy day!
The other topics include the education of architects, technical devices like sundials and water clocks, mechanical devices for war, and the ethnography of various peoples.
Then he learned to draw the various designs of sundials, indicating the hours exactly, and to measure the height of objects by geometric rule.
He also mentioned how to apply this method in surveys and how to expand the principles of the gnomon to make sundials.
A sundial is a wholly unreliable method of measuring time, and so is a clock.
Improved communications and better clocks revealed another problem with using a sundial as a clock.
