30 EXCURSIONS ROUND LONDON. 



If the beneficent author of nature had 

 intended nothing beyond the mere exercise 

 of our organs, he would only have establish- 

 ed between them and external objects, the 

 relations of absolute necessity. But, like 

 favourite children, we have been treated 

 with distinguished bounty, and loaded with 

 innumerable benefits; since to the first of 

 these relations the Almighty has superadded 

 those of utility and pleasure, which so 

 agreeably diversify our enjoyments. 



Let us first remark, what is essential to 

 the existence of the relations of absolute 

 necessity with respect to the organs of 

 hearing. It is only requisite that different 

 species of sonorous bodies should exist, and 

 that the air, instead of operating as an ob- 

 stacle to the propagation of sounds, should 

 facilitate their transmission. 



We are equally embarrassed to determine 

 the nature of sound, as to discover that of 

 light. In what does sound consist? How 

 is it produced: How does it happen that 



the 



