DIALS AND CLEPSYDRX. 47 



to mark the passage of time, and are in common use even at the 

 present day. Every country tavern is furnished with its meridian 

 or noon-line, which oftentimes is nothing more than a scratch 

 ov mark in the floor, and the gnomon, or shadow-stick, is the side 

 of, a window or door. In our younger days, we have watched 

 with far more interest, the shadow approach the humble line 

 drawn on the floor of a tinker's shop, than in more mature years 

 the steady passage of a star over the wires of a transit telescope. 

 And we have not forgotten those days of sun-dial memory, when 

 we were, unconsciously, children playing with time. We find 

 allusions to the dial in the Old Testament. The dial of Ahaz, 

 which was, undoubtedly, a large public edifice. Such was the 

 dial constructed by Dionysius, and such the dial used by the 

 Chinese, and in India. Sun-dials were liable to many objections ; 

 they could only be used when the sun was shining, and conse- 

 quently at night, or in cloudy weather they were worthless. The 

 Clepsydra, or water-clock, was therefore invented at an early date. 

 It i said that they were found among the ancient Britons, at the 

 time of the invasion by Julius Caesar. 



The first water-clocks were made of long cylindrical vessels, 

 with a small perforation at the bottom. These being filled with 

 water, marked the passage of time by the descent of the fluid 

 column. Various ornamental contrivances were subsequently 

 introduced, but they were all dependent upon the same principle. 



We will imagine one of the early philosophers, with his water- 

 clock, starting the stream when some well known star was 

 occulted, or hidden by a distant object, the tube being long enough 

 to continue the stream until the next night. As the heavens 

 move on, we find him watching the descent of the liquid, and at 

 the approach of the succeeding evening, when the same star is 

 again occulted by the same object, he marks the level of the liquid 

 in his tube, and selecting another star, for the first has gone out 

 of sight, he fills the tube, and at the given signal, when the star 

 passes behind the hill, or other occulting object, he permits the 

 water to flow. On the succeeding evening, as this star is again 

 hidden, he observes the fluid, and finds it at precisely the same 

 level as before, and thus arrives at the conclusion that the star* 



