MUSIC. 291 



Sound. 



All sound travels at the same rate, (1142 feet per 

 second, or thirteen miles per minute,) a whisper, as 

 far as it goes, as fast as the report of a cannon. It 

 also describes equal spaces in equal times. 



The strength of sound is greatest in cold and 

 dense air, and least in that which is warm and rare- 

 fied. During Captain Parry's first voyage, in lat. 

 74 30' N., people might often be heard conversing 

 distinctly, in a common tone of voice, at the distance 

 of one mile. 



At Port Bowen, during Captain Parry's third 

 voyage, it was found two persons could keep up a 

 conversation with great facility between two stations 

 at the measured distance of 6696 feet, or about 1 

 statute miles. The thermometer at 18 below zero, 

 or 50 below the freezing point. 



Sound through Solid Bodies. 



A shock so slight as that produced by the head of 

 a pin struck against one end of a long beam, is dis- 

 tinctly transmitted to the other end ; indeed vibrating 

 motions may be propagated along the substance of 

 solid bodies to an immense extent.* 



Uncertainty of Sound. 



In listening to sounds, we are deceived as to .the 

 quarter from whence they proceed, by the change 

 produced in the direction of the sonorous waves by 

 intervening obstacles, so that we mistake the reflected 

 for the radiated vibrations, echo for direct sound. 



* It is probable that a smart blow on one end of a solid bar of 

 iron, of two inches in diameter and ten miles long, would be 

 heard almost instantaneously at the other extremity ; but for the 

 success of such an experiment it would probably require the cli- 

 mate and silence of Melville Island. 

 u 2 



