Proceedings of the Polytechnic Association. 1039 



In early times the term " liorologium" was applied to every instru- 

 ment that in any way measured time, whether sun dial, clepsydra, 

 clepsammia or clock. The word " clock" originally meant only the 

 bell used for ringing out the hour, determined by the horologe, and 

 was so applied up to the fifteenth century. The first mention of the 

 word is said to be in a work by Dr. Reginald Peacock, written in 

 1449. 



When Dion, after- delivering the Syracusans, spoke to them on tlie 

 tyranny of Dyonisius, Plutarch says he stood on the top of a lofty 

 sun-dial erected by the tyrant. Many nations had columns erected 

 for casting the sun's shadow, and it seems probable that this was the 

 earliest attempt at time-keeping ; yet some authors claim the clepsy- 

 dra to have been used long before the sun-dial. 



In % Kings, xxii, 11, we read : "And Isaiah the prophet cried 

 unto the Lord, and he brought the shadow ten degrees backward by 

 which it had gone down in the dial of Ahaz." Now Ahaz was 

 King of Judah from 741 to Y26 B. C, while it is very generally 

 admitted that the dial, with a gnomon for casting the sun's shadow, 

 was the invention of Anaximander, who was born 610 B. C, and 

 could hardly liave invented the dial 150 years after Ahaz's day. 



One author I consulted tells me that " dial" and " degrees" are 

 translated from the same word in the original ; but a scholar, to 

 whom I put the question, said that " degrees" was translated from 

 the word that represented the pole, or whatever it was that cast the 

 shadow. 



It will not be out of place here to explain the mechanism of the 

 dial of Ahaz, presuming his to be like others of his day and genera- 

 tion. Tlie first requisite was an open and level plot of ground of 

 the proper dimensions ; then a very straight and smooth post from 

 fifteen to twenty feet in height, erected near its southern limits next 

 a meridian line drawn by the aid of the north star, and lastly a 

 series of varying semicircles by which to gage the length of the 

 sun's shadow. The time was determined by the length of the 

 shadow cast, and not by the position of the shadow and the distance 

 passed over. 



The first sun-dial was set up at Rome by L. Papirius Cursor 301 B. 

 C, and the next near the Rostra by M. Valerius Mesela, the consul 

 who brought it from Catana in the first Punic war, 267 B. C. The 

 Romans, at this time, were not aware that a dial, true for Sicily, was 

 not true for the latitude of Rome. The sun-dial, being of no use at 



