HEARING. 63 



any other loud sound is produced, you are utterly 

 unable to tell on which side of the house the 

 sounding body is situated. If there are windows 

 only on one side of the apartment, you get a 

 notion of the direction of the sound; but it is 

 probable that notion is a wrong one, because 

 the room has four sides; and unless you have 

 something else to guide your conclusion, you in- 

 variably suppose that the sound is upon the side 

 where the open windows are. 



The ear is a beautiful instrument, and the de- 

 gree of nicety to which it can be educated is quite 

 astonishing ; but still we are unable so to under- 

 stand the instruments, or analyze the process of 

 hearing, as to be able to say in what it consists ; 

 and, as a direct means of observing nature, plea- 

 sure rather than information is what it brings us. 

 We know that sound is produced by some sort of 

 motion in the sounding body, and that it is pro- 

 pagated through the air, so that what we imme- 

 diately hear is really the air, and not the body, 

 the motion of which first originates the sound. 

 It also goes in the direction opposite to that of the 

 motion by which it is originally produced ; and 

 against the motion of the air which is the medium 

 of it, though that motion both retards its progress 

 and diminishes its loudness, yet not to the 

 same extent as the motion of the air. The wind 

 renders sound less audible ; but the audibility is 

 diminished in the direction of the wind as well as 

 in the opposite direction, though not quite to the 

 same extent. When a coach is on the road, and 

 not in sight, we can hardly tell whether it is 

 before us or behind ; and if there be any thing near 

 us that will echo the sound, the sounding body 

 G 2 



