74 THE POPULAR SCIENCE MONTHLY. 



cone to your mouth and sing into it. The sonorous vibrations enter 

 the side A of the box, and, striking on the thin rubber, force this in 

 and out. When it goes in, a puff of gas is driven out of the other 

 partition, S, of the box, and the flame F jumps up. When the sheet 

 of rubber vibrates outward, it sucks the gas into the box JB, and the 

 flame F jumps dovrn. Therefore, on singing into tne funnel, you will 

 see in the mirror the smooth top-border of the luminous band bro- 

 ken up into little tongues or teeth of flame, each tooth standing for 

 one vibration of the voice on the rubber partition. 



Place a lamp-chimney around the flame, should the wind from the 

 twirling mirror agitate it, and be careful not to have the flame too 

 high. 



Experiment 113. — Another way of showing the vibrations of the 

 flame is to burn the jet of gas at the end of a glass tube stuck into the 

 end of a rubber tube attached to F. Now sling the tube round in a 

 vertical circle, and you have an unbroken luminous ring ; but as soon 

 as you sing into the cone this ring breaks up into a circle of beads of 

 light, or sometimes changes into a wreath of beautiful little luminous 

 flowers, like forget-me-nots. To make this experiment, you will be 

 obliged to have a tube with a larger opening than that at F. 



This instrument will afford you many an hour of instruction and 

 amusement. We have only space to show you a few experiments. 

 Others will suggest themselves whenever you use it. 



Experiment llJf.. — Sing into the funnel the sound of oo as in pool. 

 After a few trials you will get a pure simple sound, and the flame will 

 appear as in Fig. 52. Some voices get this figure more readily by sing- 

 ing E. 



Experiment 115. — Twirling the mirror with the same velocity, grad- 

 ually lower the pitch of the oo sound till your voice falls to its lower 

 octave, when the flame will appear as in Fig. 53, with half the number 

 of teeth in Fig. 52, because the lower octave of a sound is given by 

 half the number of vibrations. 



Experiment 116. — Sing the vowel-sound o on the note and you will 

 see Fig. 54 in the mirror. This evidently is not the 



py figure that would have been made by a simple vibra- 



*^^M- — !- ~\ tion. It shows that this o sound is compound, and 



formed of two simple sounds, one the octave of the 

 other. The larger teeth are made by every alternate vibration of the 

 higher simple sound acting with a vibration of the lower, and thus 

 making the flame jump higher by their combined action on the mem- 

 brane. 



Experiment 117. — Fig. 55 appears on the miiTor when we sing the 

 English vowel a on the note f. 



Experiment 118. — Fig. 56 appears on the mirror when we sing the 

 English vowel a on the note c. 



Examine attentively Fig. 55. This shows that the English vowel a 



