USES OP THE PARTS IN THE EAR. 327 



should imagine that the general surface of the 

 membrane was unsuitable for so great a variety 

 of compound motions, the chords visible upon its 

 interior surface may be considered sufficient to 

 allow it to correspond with every possible variety 

 of note. (See fig., vol. i., p. 50.) 



How satisfactory soever the ingenious experi- 

 ments in acoustics and with musical instruments 

 may be, there is a difficulty which has not been 

 met in assigning the offices to some of the parts 

 in the ear. The chain of bones in the tympanum 

 undoubtedly communicates the sounds from the 

 membrane of the tympanum to the proper seat 

 of the sense, the labyrinth ; and nothing is more 

 easy than to conceive that the membrane of the 

 tympanum, receiving an impulse, like a sail flap- 

 ping by the wind, should communicate the same to 

 tlie malleus and in succession to the other bones. 

 But the difficulty arises from considering that it 

 is not a mechanical impulse which is communi- 

 cated, but a motion of sound. When philosophers 

 teach us the nature of sound by throwing a peb- 

 ble into a still pond of water and making us ob- 

 serve the concentric undulations : or by striking 

 a cord and observing the motions which accom- 

 pany the sound, and showing the harmonic sub- 

 divisions, we seem to have overcome all the diffi- 

 culties of the science. But we encounter new 

 difficulties when we are forced to conclude that 

 all the combinations of sound in an orchestra, for 



