xom 



PRODUCED BY MIvYNS OF T 



181 



ag-ain put together so as to give to the tube a position which is 

 ar to, but not exactly, its proper one, a long time will often elapse 

 fore it begins to sound again. But if the notes of the gamut 

 loudly sung or whistled in the vicinity of the tube, it will 

 and immediately, when the note is sounded which the tube 

 ;elf produces; this is because the air in the tube is thrown into 

 bration, and thus it produces the intermittent flow of the gas. 

 inversely, if the flame has not the most suitable position, the 

 te given out by the tube may be silenced immediately by 

 unding strongly a note which is a little higher or lower than 

 e note of the tube ; here sonorous waves enter the tube in 

 < me what slower or quicker succession than those which are pro- 

 :iced within : the regular interruption of the flow of the gas 

 bm the jet is interfered with, and the production of sound 

 !ases. 

 I 



! The most usual mode of producing vibrations of 



ohimns of air in tubes, and the one which is chiefly used 



musical instruments, is to blow air across the aper- 



i.re of a tube. With the help of an indiarubber tube, 



FIG. 230 (an. proj. real size}. 



end of which is slightly compressed with the fingers 

 H as to obtain a narrow, elongated aperture, notes may 

 \ produced from tubes which are either open at both 

 (|ds or at one only, and also from various hollow vessels 

 (ottlcs, c.). 



