48 Curiosities of Sound. 



maximum of resonance when twice the length of a closed one. 

 The strengthening by resonance of feeble sounds not previously 

 heard or noticed, is the cause of the " sea music," which 

 children are so fond, of when cowry shells are held to their 

 ears. Caves and rocks resound, to the noise of waterfalls, and 

 deep wells to the fall of objects on the water which they contain. 



Amongst the most beautiful and curious of the strange 

 ways of sound, we must allude to singing and to sensitive 

 flames. If a glass or metal tube, two or three feet long, is 

 held at a proper height — easily found by trial — over a small 

 jet of gas, a musical note is heard ; and if the experiment is 

 made on a large scale, the sound is violent. The musical note 

 arises from a series of impulses communicated by the flame, 

 which is a rapidly twinkling one, to the air. Hydrogen gas 

 answers for these experiments better than coal gas. 



The sensitive naked flames are the most extraordinary and 

 apparently magical things. A broad fish-tail flame exhibits 

 the phenomena to a considerable extent. Such a flame will 

 jump and put forth tongues in sympathetic response to a par- 

 ticular set of vibrations. Professor Tyndall showed that, by 

 producing a slight flutter with a blowpipe in a candle-flame, it 

 was made sensitive, and jumped when a whistle was sounded. 

 By adding to the pressure, and obtaining flaring flames from 

 common fish-tail and bat's-wing burners, they became sensitive 

 to whistles, and put forth curious tongues; and striking a 

 distant anvil with a hammer gave similar results. By using a 

 single orifice burner and suitable pressure, flames eighteen inches 

 long were obtained, smoking copiously, and remarkably sensitive 

 to sound vibrations of the right quality. By sounding a whistle, 

 Professor Tyndall caused the flames to change instantly, and 

 become short, forked, and brilliant. Another flame exhibited 

 by the professor to his wonderstruck audience was twenty-four 

 inches long, and by the slightest tap on a distant anvil it was 

 reduced to seven inches. Dropping sixpence from the hand 

 twenty yards off was sufficient to knock the flame down; the 

 creaking of boots, the rustle of a lady's dress, the patter of 

 rain, and the tick of a watch — all influenced it in a striking 

 way. When lines of poetry were recited, the flame nodded to 

 some sounds, took no notice of others, and when the tones of 

 the voice were most in sympathy with it, " its obeisance was 

 profound." 



Here we must leave Professor Tyndall and his most in- 

 teresting book, intending, however, to take another oppor- 

 tunity of recurring to moro of the " Curiosities of Sound," to 

 whose wonders, we hope, the present pages may prove an 

 introduction for those who love science in its recreative aspects 

 and lighter moods. 



