MUSICAL SOUNDS FROM VIBRATION OF AIR. 183 



It is owing to this property of sounding bodies 

 that singers with great power of voice are able to 

 break into pieces a large tumbler glass, by singing 

 close to it its proper fundamental note ; and it is 

 from the same spmpathetic communication of 

 vibrations that two pendulum clocks fixed to the 

 same wall, or two watches lying upon the same 

 table, will take the same rate of going, though 

 they would not agree with one another if placed 

 in separate apartments. Mr. Ellicott even 

 observed that the pendulum of the one clock will 

 stop that of the other, and that the stop ped 

 pendulum will, after a certain time, resume its 

 vibrations, and in its turn stop the vibrations of 

 the other pendulum. 



The production of musical sounds by the vibra- 

 tions of a column of air in a pipe is familiar to 

 every person, but the extraordinary mechanism by 

 which it is effected is known principally to 

 philosophers. A column of air in a pipe may be 

 set vibrating by blowing over the open end of it, 

 as is done in Pan's pipes ; or by blowing over a 

 hole in its side, as in the flute ; or by blowing 

 through an aperture called a reed, with a flexible 

 tongue, as in the clarionet. In order to under- 

 stand the nature of this vibration, let AB, Fig. 

 41, be a pipe or tube, and let us place in it a 

 spiral spring AB, in which the coil or spire are at 

 equal distances, each end of the spiral being 

 fixed to the end of the tude. This elastic spring 

 may be supposed to represent the air in the pipe, 

 which is of equal density throughout. If we 

 take hold of the spring at m, and push the point 

 m towards A and towards B in succession, it will 

 give us a good idea of the vibration of an elastic 

 column of air. When m is pushed towards A, 



