Around 300 BC, the Babylonians developed a hemispheric sundial, which according to the Arab astronomer Al-Battani, was still in use in Muslim countries during the 10 th Century. Other refinements included the Romans invention of a portable sundial that allowed seasonal and latitudinal adjustments. Although sundials of elaborate design were produced during the Renaissance, the invention of the clock signaled the end of sundials as the common method of telling time. However, European clockmakers sometimes sent small sundials with their clocks to the American colonies to ensure that the clocks were set properly. And in Europe, there were sundials installed on clock towers to verify the accuracy of the clockwork.
Sundials indicate apparent solar time, while clocks are regulated to indicate mean solar time.
Another form of sundial uses a metal sphere into which is projected the shadow of the sun. This type is somewhat easier to read with accuracy than the horizontal kind. Although there is a resemblance, the two are not the same. An armillary sphere is a medieval device used to show the important celestial meridians and equators. This means the gnomon should point to the North Star.