VIBRATION IN WATER. 5 



the water, though undistinguishable to us. Who has 

 not observed the terrified agitation of the fish, as far 

 as the eye can penetrate the water, at the least per- 

 ceptible vibration caused by a stamp of the foot at 

 the bottom of a punt or boat ? We have frequently 

 ourselves seen fish clear the water altogether in 

 ponds and lakes at a distance of forty yards from the 

 point or focus of concussion. That sound is not 

 communicated only by the external ear may be seen 

 by the following experiment : Take an ordinary 

 tuning fork, strike it, and take the full volume of the 

 sound quite close to the ear, then strike again and 

 place the handle against or between the teeth, when, 

 though at some distance from the ear, the sound will 

 not be found to be diminished. Vibrations vary in 

 intensity according to the degree of solidity and 

 density of the conductive bodies. Thus, we are told 

 that in the atmosphere sound travels at the rate of 

 something like one thousand feet per second on 

 bright, clear days, but 1,100 in murky, dull, and 

 hazy weather. In water, however, sound travels very 

 much quicker, being at the rate of 5,000 feet per 

 second, and where wood is the medium quicker still, 

 16,000 feet per second being its rate of progress. If, 

 therefore, a solid substance is the conductor of sound, 

 it naturally follows that it will become more distinct. 

 The operator upon the violin has thus a keener per- 

 ception of the various strains of the instrument than 

 the ordinary listener, since wood is the sole conductive 

 body in his case. The organ of hearing being en- 

 closed in the hard case of the head is, in the case of 



