124 TERRESTRIAL ADAPTATIONS. 



atmosphere? Or is not the only intelligible 

 account of the matter, this, that one was made 

 for the other : that there is a mutual adaptation 

 produced by an Intelligence which was ac- 

 quainted with the properties of both ; which 

 adjusted them to each other as we find them 

 adjusted, in order that birds might communicate 

 by song, that men might speak and hear, and 

 that language might play its extraordinary part 

 in its operation upon men's thoughts, actions, 

 institutions, and fortunes ? 



The vibrations of an elastic fluid like the air, 

 and their properties, follow from the laws of mo- 

 tion ; and whether or not these laws of the motion 

 of fluids might in reality have been other than 

 they are, they appear to us inseparably connected 

 with the existence of matter, and as much a thing 

 of necessity as we can conceive any thing in the 

 universe to be. The propagation of such vibra- 

 tions, therefore, and their properties, we may at 

 present allow to be a necessary part of the 

 constitution of the atmosphere. But what is it 

 that makes these vibrations become sound ? How 

 is it that they produce such an effect on our 

 senses, and, through those, on our minds ? The 

 vibrations of the air seem to be of themselves no 

 more fitted to produce sound than to produce 

 smell. We know that such vibrations do not 

 universally produce sound, but only between 

 certain limits. When the vibrations are fewer 



