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THE POPULAR SCIENCE MONTHLY. 



in a second in all directions through the surrounding air. They soon 

 reach the drum-skin of the ear. The latter, being elastic, moves in 

 and out with the air which touches it. Then this membrane, in its turn, 

 pushes and pulls the little ear-bones 500 times in a second. The last 

 bone, the little stirrup, finally receives the vibrations sent from the 



Fig. 4. 



violin-string, and sends them into the fluid of the inner ear, where 

 they shake the fibres of the auditory nerve 500 times in a second. 

 These tremors of the nerve — how we know not — so affect the brain 

 that we have the sensation which we call- sound. 



In Chapter V. it is shown that the mechanical actions, which finally 

 result in giving us the sensation of sound, always have their origin in 

 some vibrating body, and that this vibrating body may be either solid, 

 liquid, or gaseous. The author, after showing that the vibrations of a 

 solid (a tuning-fork) and of a liquid (water running through a toy 

 flageolet) give origin to sound, presents .to his readers — 



An Experiment made with a Whistle and a Lamp-Chimnet, 



SHOWING that, as IN WiND -INSTRUMENTS, A ViBRATING COLUMN OF 



Air may originate Sonorous Vibrations. — Experhnent 33. — The 

 chimneys of student-lamps have a fashion of breaking just al the thin, 

 narrow part near the bottom. Such a broken chimney is very useful 

 in our experiments. At A, in Fig. 25, is such a broken chimney, closed 

 at the broken end with wax. A cork is fitted to the other end of the 

 chimney, and has a hole bored through its centre. In this hole is in- 

 serted part of a common wooden whistle. At JB is an exact represen- 

 tation of such a whistle, and the cross-line at G shows where it is to 

 be cut in two. Only the upper part is used, and this is tightly fitted 

 into the cork. 



