:378 



VIBRATIONS OF AIR IN TUBES. 



consequence of the vibrations produced in the air in 

 the tube. 



For a common (a 1 ) tuning fork a tube is required which is eithei 

 19 cm '5 long if closed at one end, or 39 cm long if open at hot! 

 ends. Tubes of about 25 mm width are the best for this experiment 

 A cylindrical jar with a foot, about 25 cm high, will serve as : 

 tube closed at one end. Water may be poured into it gradually unti 

 the sound of the fork reaches its greatest intensity, that is, until th 

 column of air in the tube has the exact length required for per 



FIG. 228 (an. proj. i real size}. 



forming vibrations of equal duration to those of the tuning-fo 

 -(fig. 228, A). A lamp cylinder will serve equally well, if a we 

 fitting cork is introduced from the wider end and pushed inwar( 

 until the column of air above it has the required length (fig. 228, 1 

 The tubes may also be made by rolling stout paper or thin cardboa 

 round a cylindrical bar of suitable thickness, and fastening the ed 

 with glue : one end may be again closed by a cork, which mn 

 however, be fixed with glue or sealing-wax. 



A remarkable method of producing a note in tub 

 open at both ends consists in allowing a small flame 

 .a gas hydrogen is the best for the purpose to buj 

 inside the tube. Such a flame will not burn long ii 

 .tube which is closed at one end, because of the impos 



