378 



Prof. Tyndall on the Action of Sonorous 



disposal than that existing in the pipes of the Institution*. I 

 enlarge the flame ; and now a slight flutter of its edge answers to 



Fig. 5. 



Fig. 6. 



the sound of the whistle. Finally I turn on gas until the flame 

 is on the point of roaring, as flames do when the pressure is too 

 great. On sounding the whistle, the flame roars, and suddenly 

 assumes the form shown in fig. 6. 



When a distant anvil is struck with a hammer, the flame in- 

 stantly responds by thrusting forth its tongues. 



An essential condition to entire success in these experiments 

 disclosed itself in the following manner. I was in a room illu- 

 minated by two fish-tail flames. One of them jumped to a whistle, 

 the other did not. The gas of the non-sensitive flame was turned 

 off, additional pressure being thereby thrown upon the other 

 flame; it flared, and its cock was turned so as to lower the 

 flame. It now proved non- sensitive, however close it might be 

 brought to the point of flaring. The narrow orifice of the half- 

 turned cock appeared to interfere with the action of the sound. 

 When the gas was turned fully on and the flame lowered by 

 opening the cock of the second burner, it became again sensitive. 

 Up to this time a great number of burners had been tried, inclu- 

 ding those with single orifices ; but with many of them the action 

 was nil. Acting, however, upon the hint conveyed in this ob- 

 servation, the pipes which fed the flames were widely opened ; 

 the consequence was that our most refractory burners were thus 

 rendered sensitive. 



The observation of Dr. Leconte is thus easily and strikingly 

 illustrated; in our subsequent and far more delicate experiments 

 the precaution just referred to is still more essential. 



* A gas-bag properly weighted also answers for these experiments. 



