390 Action of Sonorous Vibrations on Gaseous and Liquid Jets. 



like a frozen band, so motionless does it appear. On stopping 

 the fork, the arch is shaken asunder, and we have the same play 



Fig. 20. 



of liquid pearls as before. Every sweep of the bow, however, 

 causes the drops to fall into a common line of march. 



A pitch-pipe, or an organ-pipe yielding the note of this 

 tuning-fork, also powerfully controls the vein. My voice does 

 the same. On pitching it to a note of moderate intensity, I 

 cause the wandering drops to gather themselves together. At 

 a distance of 20 yards, my voice is, to all appearance, as 

 powerful in curbing the vein and causing its drops to close up 

 as when I stand close to the issuing jet. 



The effect of beats upon the vein is also beautiful and instruc- 

 tive. They may be produced either by organ-pipes or by tuning- 

 forks. Before you are two forks, one of which vibrates 512 

 times, and the other 508 times in a second. You will learn, in 

 our next lecture, that when these two forks are sounded together 

 we ought to have four beats in a second. I agitate the two forks, 

 and find that the liquid vein gathers up its pearls and scatters 



