126 OBSERVATIONS ON VENTRILOQUISM, 



of the lips : there are but few perfons, I imagine, who have? 

 not fome time or other witncfled an incident, which mew's 

 Inftance. the vulgar notion to be erroneous in this particular. For if a 



man ftanding in a clofe apartment fhould happen to apply his 

 face to a loop hole, or narrow window, in order to fpeak to 

 fome perfon in the open air, a by-ftander in the room with 

 him will hear his voice, not indeed in its natural tone, but as 

 if it were fmothered by being forced to iffue from a hollow 

 cafe ; but the circumftance of his words being heard diftincllv, 

 by one who cannot receive them from his mouth, proves the 

 vibrations requifite for their production to be conveyed through 

 thefolid parts of the fpeaker's body, agreeably to the preced- 

 ing afTertion. The reafon why we generally conclude the 

 voice to be confined to the opening of the mouth, appears to 

 be this. Thofe pulfes which efcape from the aperture are the 

 ftrongeft, they therefore furpafs the weaker vibrations of the 

 contiguous parts ; for when a number of founds moving in 

 different directions ftrikes the ear at the fame inftant, the 

 hearer does not notice their feveral places, but refers all of 

 them to the quarter in which the mod powerful is perceived. 

 For inftance, when a man ftands at a fufficient diftance from 

 an extenfive obftacle, his words are anfwered by an echo j 

 but let him make a loud uninterrupted noife, neither he nor 

 any body near him hears two voices whilft his continues, but 

 as foon as the noife ceafes the echo is perceived. This does 

 not happen becaufe the one begins the moment the other ends ; 

 but the reflected found being the weaker of the two, it is 

 fmothered by that which precedes it. 

 Effect of undlf- " We have feen in what manner feeondary or reflected founds 



ting U iftiedecho» arefmothered by their principals; but though the places of 



upon the voice J r . \ ' b . J; 



or an inftru- fuch founds are not recognized by the ear, their effects do not 



mcnt » die away unnoticed : for the reverberated pulfes mingle with 



thofe which come immediately from the founding body, and 



thereby alter the fenfation, which, without their interference, 



would be lefs compounded. This is the reafon why the fame 



mufical initrument has one tone in a clofe chamber, where its 



notes undergo a multiplicity of reverberations, and another in 



the open air, where the reflections are few in comparifon. 



Cafe of an ora- " ^ ut ** * s t ' me to apply the preceding facts to the fubjecl in 



tor j hand ; and it will be proper to begin with a familiar example. 



When an orator addrefles an audience in a lofty and fpacions 



room, 



