SCIENTIFIC TRACTS. 



NUMBER XIII. 



SOUND. 



I. VIBRATIONS OF SOUNDING BODIES. 



EVERY one has noticed that, in many cases, where 

 sound is produced, there is a trembling or vibration of 

 the sounding body. This is evidently the case when a 

 heavy bell is struck, or the large strings of a viol are 

 sounded. In some other cases, as in the flute and whis- 

 tle, these tremblings are less obvious. They are not 

 however less real. Sound is, in all cases, produced by 

 vibrations in a sounding body, occasioning similar vibra- 

 tions in the air. 



Various facts will, at once, occur to the reader, illus- 

 trative of this principle. 



The vibrations of a large bell, or of a viol string, as 

 above remarked, are visible. 



The head of a drum is thrown into a state of vibration 

 by the strokes of the drumstick. 



If a tuning fork, when sounding, is touched to the 

 teeth, the vibrations are sensibly felt. 



If the tuning fork or a bell be touched with the finger, 

 so as to check these vibrations, the sound is instantly 

 stopped . 



In the rctd stops, as they are called, of an organ, the 

 sounds are produced by the vibrations of thin slips of 

 metal, fastene'd^t one end. 



If a large glass vessel, partly filled with water, is made 

 to sound by rubbjlig the edge with a wet finger, the vibra- 

 tions produced are made evident by peculiar and beauti- 

 ful undulations in the water. If the upper part of the 



VOL. i. NO. xin. 28 



