Abstract
Three water clocks of Han dynasty production are still in existece. All of them are made of bronze. In this treatise, I study them in detail and speculate on the circumstances of their actual use in the time of their production.
Then, on the basis of these existing water clocks and related documentary records, I examine the origin and the course of development of water clock.
Though, I don't specialize in the study of Japanese history, I additionally presents in this treatise a secondary review of Asuka water clock. For Asuka water clock, which was excavated recently from the ruins of Mizooch (水落)in Nara prefecture, a national institution has prepared a replica. I, however, believe that this peplica is not accurate. I therefore suggest an alternative water clock model which I think fits to the characteristics of the ruins.
