314 DETAILED SYNTHESIS. 



action needed to keep it tense under the influence' of 

 the vibration. 



Remark. Thus muscular action and sensation is again used to de- 

 termine force, as it always is in the body. According to the action of 

 the muscles of the middle ear, so are the sensations they will cause. 



875. THE PITCH OP VIBRATIONS is DETERMINED by 

 the number of vibrations in a given time. 



876. Illus. If a string of a certain tensity is vibrating a certain 

 number of times in a second, one of half its length at the same tensity 

 would vibrate twice as many times in a second, and its sound would be 

 an octave higher. 



877. IN THE SPIRAL PARTITION BETWEEN THE SCALJ3 



OF THE COCHLEA exist all the requisites for appreciating 

 the rapidity of vibrations ; for from bottom to top the 

 scalas and their partition diminish by a perfect gradation 

 corresponding to every possible period or pitch of vibra- 

 tion of the^air. 



878. Him. If a musical instrument is sounded near a harp or a 

 piano, a string of these instruments, corresponding in proportionate 

 length, and being of course in harmony with the instrument sounded, 

 will also be thrown into vibration, and cause a sound. 



879. THE QUALny OP VIBRATIONS is determined by 

 some as yet un distinguishable characteristic of the vi- 

 brations, different in case of almost everything causing 

 sound. 



880. Remark. Herein is a wonder of wonders that there is some- 

 thing so perfectly evident, and yet eluding our grasp most effectually ! 

 It is also still more strange that this can be so when there are so many 

 millions of different qualities hi sounds and of course vibrations, in every 

 human voice not only, but that of every bird and even of every insect, as 

 well as in all the noises of dumb nature. 



881. THE NERVES CONNECTED WITH THE 

 AND THE SEMICIRCULAR CANAL are constructed for the 

 purpose of appreciating the qualities of vibrations, the 

 effects of which reach them; for there is no other office 



875. Howls ? 876. Illustrate. 877. What exist -? 878. Illustrate. 879. How 

 determine ? 880. What wonderful ? 881. What said of ? 



