ON CHINESE HOROLOGY, ETC. 219 



nected with a furnace, and surrounded by heated water. Chau flourished 

 eleven centuries before our era. The forms of the apparatus have been 

 various, but they generally consisted of an upper and a lower vessel, 

 always of copper, the former having an aperture in the bottom, through 

 which water percolated into the latter, where floated an index, the 

 gradual rise of which indicated successive periods of time. In some 

 this was reversed, the float being made to mark time by its fall. A 

 portable one was occasionally employed, in ancient times, on horseback, 

 in military tactics. Instruments constructed on the same principles 

 with the above were in use among the Chaldeans and Egyptians at an 

 early period — that of Ctesibus, of Alexandria, being an improvement 

 over those of more ancient times. The invention of Western Asia was 

 doubtless wholly independent of that ot the East, both being the result 

 of similar wants. Clepsydras were subsequently formed of a succession 

 of vessels communicating by tubes passing through dragons, birds, &c, 

 which were rendered still more ornamental by the indices being held in 

 the hands of genii. 



The earliest application of motion to the clepsydra appears to have 

 been in the reign Shuenti (1*26-145 a. d.), by Tsianghung, who con- 

 structed a sort of orrery representing the apparent motion of the 

 heavenly bodies round the earth, which was kept in motion by drop- 

 ping water. There is reference, also, to an instrument of this description 

 in the third century. 



In the sixth century an instrument was in use which indicated the 

 course of time, by the weight of water, as it gradually came from 

 the beak of a bird, and was received into a vessel on a balance, every 

 pound representing a kih. About this time mercury began to be 

 employed instead of water, which rendered the aid of heat in winter 

 unnecessary. Changes were made also in the relative number of kih 

 for day and night, so as to vary with the seasons. 



As in Europe, monks of the Roman church devoted considerable at- 

 tention to mechanical inventions, especially in the construction of instru- 

 ments for measuring time for the regulation of their worship and vigils ; 

 in like manner, also, Buddhist monks, in their silent retreats, but at an 

 earlier period, similarly occupied themselves, and for the same purposes. 

 Several instruments, designed as time-pieces, the invention of priests, 

 are mentioned in Chinese history. They present nothing novel, how- 

 ever, with the exception of one, which is nothing more than a perforaled 

 copper vessel, placed in a tube of water, which gradually filled and sunk 

 every hour, requiring, of course, frequent attention. Although their 

 knowledge of hydrodynamics has ever been very limited, the Chinese 

 appear to have been the first to devise that form of clepsydra to which 

 the term water-clock is alone properly applied ; that is to say, composed 

 of apparatus which rendered watching unnecessary by striking the 

 hours. Until the commencement of the eighth century, the persons 

 employed to watch the clepsydra in palaces and public places struck 



s 2 



