USES OF THE PARTS IN THE EAR. 329 



that board will be given out to the atmosphere, 

 and we shall hear the concert, that is, the com- 

 bined sounds of the instruments, although neces- 

 sarily faint. Here, then, the music must have 

 been conveyed along the rod ; and we have 

 another proof that sound cannot consist of those 

 coarser movements ascertained by the other 

 senses, but of something so infinitely more minute 

 that the particles in the rod may convey distinct 

 vibrations simultaneously. These considerations 

 certainly countenance our belief, that however 

 fine the chain of bones may be which, passing 

 through the tympanum, communicates between 

 the external and internal ear, it is yet capable 

 of a variety of motions corresponding with the 

 sounds, of which the ear is susceptible. 



What, then, is the meaning of this very obvious 

 mechanical structure in the chain of bones in these 

 little levers and their attached muscles? (See 

 fig. p. 47, vol. i.) Are not the three muscles at- 

 tached to the bone that is fixed to the membrane 

 calculated to affect the tension of the membrane? 

 If we take the illustration in the text, we must 

 remember that the military drum is not so simple 

 as it has been represented. The chords or braces, 

 which pass outside the drum obliquely, are tight- 

 ened by pushing down the knots of buflf leather, 

 and this not only stretches the parchment head of 

 the drum, but tightens the snares or cords which 

 run over the parchment of the reverse of the 

 drum. In the military drum, it is the blow on 

 29* 



