90 NATURAL HISTORY. 



I suppose there is some vault, or hollow, or isle, 

 behind the wall, and some passage to it towards the 

 farther end of that wall against which you speak ; 

 so as the voice of him that speaketh slideth along the 

 wall, and then entereth at some passage, and com- 

 municateth with the air of the hollow ; for it is pre 

 served somewhat by the plain wall ; but that is too 

 weak to give a sound audible, till it hath communi 

 cated with the back air. 



149. Strike upon a bow-string, and lay the horn 

 of the bow near your ear, and it will increase the 

 sound, and make a degree of a tone. The cause is, 

 for that the sensory, by reason of the close holding, 

 is percussed before the air disperseth. The like is, 

 if you hold the horn betwixt your teeth : but that is 

 a plain delation of the sound from the teeth to the 

 instrument of hearing ; for there is a great inter 

 course between those two parts ; as appeareth by 

 this, that a harsh grating tune setteth the teeth on 

 edge. The like falleth out, if the horn of the bow 

 be put upon the temples ; but that is but the slide 

 of the sound from thence to the ear. 



150. If you take a rod of iron or brass, and hold 

 the one end to your ear, and strike upon the other, 

 it maketh a far greater sound than the like stroke 

 upon the rod, made not so contiguous to the ear. 

 By which, and by some other instances that have 

 been partly touched, it should appear, that sounds 

 do not only slide upon the surface of a smooth body, 

 but do also communicate with the spirits, that are 

 in the pores of the body. 



