536 



HISTORY OF SCIENCE. 



In general, however, a cord does not thus vibrate, but divides into a 

 number of equal parts, as shown in Fig. 251, which represents the 

 method of causing a stretched wire to divide into several vibrating 

 segments. The tip of the finger is gently pressed at some point of 

 aliquot division as at K 2 , where K K 2 is one-third of the whole length. 

 When a violin-bow is drawn across the middle of the segment, as at 



FIG. 251. 



s x , the wire divides itself into the segments s l , S 2 , s 3 , and the sta- 

 tionary points, K 2 , K 3 , are called the nodes. A method of exhibiting 

 the positions of the nodes in a vibrating wire was devised by Sauveur 

 (1701), and is shown by Fig. 252, where we have represented the 



FIG. 252. 



division of a wire into four vibrating segments. Little pieces of paper 

 are first placed astride the wire in various places. When the vibrations 

 are excited by drawing the bow across the middle of the first segment, 

 all the riders are thrown off the vibrating parts of the wire, while those 

 which happen to be placed at the nodes, K 2 , K S , remain stationary. 



