1040 Teaxsactioxs of the Amebic an Institute. 



night or in cloudy weatlier, did not come into so general use as the 

 clepsydra, although much more reliable as a time-keeper when it 

 could be used. 



Authentic representations of the clepsydra are very rare, and the 

 name of the inventor or date of its advent, are not recorded. Yitru- 

 vius, a distinguished Ronjan architect, handed down valuable draw- 

 ings and descriptions of them, but they have nearly all been lost. 



Reed says that in the most remote ages, long before sun-dials were 

 invented, water-clocks had been made, and were used in China, 

 India, Chaldea, Egypt, and Plato introduced them into Greece. Ono 

 is represented at the Hippodrome, in Constantinople, in the form of 

 an oviform vase. It was mounted on an axis with a handle for rever- 

 sion, and the time it took for the water to run out was noted. The 

 simplest form of clepsydra was a cylindrical vessel with a float loosely 

 fitting its interior, from which rose a vertical gauge marked with the 

 liours, which, by its gradual ascent as the water entered, showed the 

 passing away of the hours with tolerable accurac}^ A similar one 

 had a fjinciful figure standing on the float and pointing with a hand 

 to the hour, on a stationary gauge. In some, the water flowed in as 

 tears from an automaton. In some a dial was attached to an axis on 

 which a chain was wound. At one end of the chain was attached a 

 float, and at the other a weight to nearl}^ balance. As the water rose 

 the shaft and dial revolved, while a pointer gave the hour. In others 

 tlie dial was fixed, and the pointer attached to the end of the axis. 

 This was the origin of our present dial. 



The first name mentioned in connection with the clepsydra, is 

 Censor Scipio Nassica, who some claim to have been the first to 

 measure time by night as well as by day, 600 B. C. 



They were introduced into Rome about 150 years B. C, and Pom- 

 pey thought them just the thing to regulate and prevent the babbling 

 of the lawyers, and he ordered them placed in the judicial courts. 

 The Ronians called this device the horologium nocturnum or night 

 clock. 



Ctesibius, a learned mechanician of Alexandria, has the honor of 

 first applying toothed wheels to clepsydra, about 200 years, B. C. 

 lie made a float with toothed column attached, to revolve a shaft 

 with a pointer and dial, but wc have a description of a clepsydra 

 made by him, which is more elaborate in design, and gives some 

 idea of the state of the arts at that day. This consisted of a 

 cylindrical column standing upon a square pedestal within M-hicli 



