Horologium

Sundials preceded all other instruments for the measurement of time. The gnomon or stocheion of the GREEKS was a perpendicular staff or pillar, the shadow of which fell upon a properly marked ground; the polos or heliotropion consisted of a perpendicular staff, in a basin in which the twelve parts of the day were marked by lines.

The clepsydra was a hollow globe, with a short neck, and holes in the bottom; it measured time by the escape of water, and was at first used like an hourglass to regulate the length of speeches in the Athenian courts. The escape of water was stopped by inserting a stopper in the mouth, when the speaker was interrupted. Smaller clepsydrata made of glass and marked with the hours were used in families. A precisely similar history applies to the horologia of ROME.

Horologium is from Latin horologium, from Greek orologion, literally 'that which tells the hour', from ora, 'hour', and -logion, that which tells, from legein to tell. Greek ora, hour, comes from the Indo-European root *yér- 'Year, season'. Derivatives: year, Yahrzeit (the anniversary of the death of a relative, observed with mourning and the recitation of religious texts), horary, hour, horologe (a device, such as a clock or sundial, or watch, used in telling time), horology (the science of measuring time, the art of making timepieces),horoscope, (these words from Greek hora, season).