12 SCIENCE OF THE GREEKS. PT. i. 



7. There are streams which have a petrifying power, and 

 convert the substances which they touch into marble. 



8. Volcanic vents shift their position ; there was a time 

 when Etna was not a burning mountain, and the time will 

 come when it will cease to burn. 



These, and other sentences of the same kind, show how 

 carefully Pythagoras and his followers must have observed 

 nature, for the changes that are going on upon the earth 

 take place so very slowly that it is only by very careful 

 comparison that we can prove they are happening at all. 

 Pythagoras was the first man who was called a philosopher , 

 or lover of wisdom. He made many discoveries about 

 musical notes, and the manner in which the different 

 musical intervals can be produced on a stretched string. 

 He was the inventor of a very simple but useful instrument 

 called the monochord, which consists of a sounding board 

 and box on which a single string is stretche/f, and having 

 a small loose piece of wood, called a bridge* , which is placed 

 under the wire to divide it into segments. Pythagoras 

 found that when he placed this bridge so as to divide the 

 wire into two parts, of which one was twice as long as the 

 other, and then struck each part, the shorter length gave a 

 note of the same tone as the longer one, but at a higher 

 pitch. If, however, he divided the string so that the two- 

 fifths were on one side and three-fifths on the other, then 

 the notes were separated by an interval of a fifth. In this 

 way, by marking a scale of divisions on the sounding board, 

 the Greek musicians were able to produce a whole series 

 of musical notes on one string. 



