Chap. XXXIII.] 



RESONANCE. 



441 



body of the sound many of its elements; while the 

 untrained person becomes conscious only of the fused 

 whole, is aware only of the synthesis and not of 

 the analysis. The details of this theory must, how- 

 ever, be sought in the systematic text-books. It is 

 referred to here only to show how a knowledge of 

 the physical aspect of the problem is necessary to a 

 good comprehension of the physiological process. 



Resonance. Sympathetic vibration offers an 

 explanation of another remarkable occurrence. Take 

 a tuning fork (B, Fig. 190) and cause it to vibrate by 

 drawing a bow across it, or by 

 striking it (the former pre- 

 ferably), the sound emitted 

 will be very feeble, and will 

 be heard only when the ear is 

 close to it. Hold it now close 

 to the mouth of the tall jar A, 

 still the sound is feeble. 

 Then from a jug pour water 

 slowly and as noiselessly as 

 possible into the jar. The 

 sound will be slightly in- 

 tensified, till, when a certain 

 quantity of water has been 

 added, the amount being de- 

 pendent upon the pitch of 

 the fork, the sound will 

 become greatly intensified so 

 as to be heard over a con- 

 siderable distance. Go on pouring in more water, 

 the loudness of the note will slowly diminish, till 

 it again becomes almost inaudible. It is evident 

 that when the column of air in the jar is of a par- 

 ticular length it intensifies the sound of the fork. If 

 one could blow across the mouth of the jar so 

 as to throw the air into vibration, the jaT itself 



Fig. 190. Eesonance. 



The fork is represented as if 

 touching the edge of the 

 jar. This should not be so. 

 It would also be better turned 

 with the front of the limb 

 facing the jar. 



