84 THE CREATION OF MATTER 



8853. In fir, along the fibre, it is 15,218 feet; in oak, 

 12,622; in pine, 10,900. Thus in water the velocity is 

 four times greater than in air ; in pine ten times ; in iron 

 nearly seventeen times. If a long iron bar be struck, 

 and an ear be applied to it at a distance, two sounds are 

 heard, one along the iron and the other later through 

 the air. Each substance has thus its own velocity with 

 which it propagates sound. Between different substances 

 the differences are great, but in the same substances in 

 the same circumstances the samenesses are perfect. Air 

 and every gas, water and whatsoever is liquid, iron and 

 all metals, fir and wood of every fibre, each and all are 

 true to their kind. So perfect is the accuracy that, 

 given the velocity of sound, through any substance at a 

 certain temperature, it would be possible to name it. 

 So perfectly, according to temperature, throughout the 

 whole realm of matter, are the elasticities and densities 

 and their relationships determined. In all this we see 

 the importance of elasticity as a property of matter, and 

 of motions advancing by waves, and not by the advance 

 of the substances. Air advancing at 800 miles an hour 

 would be irresistible. But through the elasticity of 

 material particles a mode of motion is obtained which 

 advances with a high velocity, and yet with a gentleness 

 imperceptible. 



Sound is enfeebled by distance according to law. This 

 is obvious to everyone endowed with the faculty of 

 hearing. There is no loss of force generated, but it is 

 evident that the volume of air acted on as the motions 

 advance is constantly increasing, and therefore the force 

 is divided among a greater number of particles. At any 

 point the intensity varies inversely as the square of the 

 distance. 



The number of the waves. Two instruments have been 



