41. Although the Greeks and Romans did much to advance water clock technology, they still continued to use shadow clocks. 42. With water clocks , and also candle clocks, modifications were made to have them make sounds on a regular basis. 43. However, the most accurate clocks available to these early navigators were water clocks and sand clocks, such as hourglass. 44. Those serving here placed four Water Clock Plates in the pond and to inform the time rang a bell. 45. Games involving members of both teams are not against the water clock and are known as " duels ". 46. The invention of the mechanical clock in the 14th century made the water clock and its feedback control system obsolete. 47. In these tablets, water clocks are used in reference to payment of the night and day watches ( guards ). 48. Alarm clocks first appeared in Ancient Greece around 250 BC with a water clock that would set off a whistle. 49. In China, as well as throughout eastern Asia, water clocks were very important in the study of astronomy and astrology. 50. _A unique illustration of a water clock design is from a 1315 Syrian treatise on the construction of mechanical devices.
