1*6 PRODUCTION OF IDEAS. SECT. XIV. 5. 



depend alone oil its elaftidty. But though the vi- 

 bration of the air is the immediate object of the 

 ienfe of hearing, yet the ideas, we receive by this 

 fenfe, like thole received from light, are only as a 

 language, which by acquired aflbciations acquaints 

 us with thole motions of tangible bodies, which 

 depend on their elafticity ; and which we had be- 

 fore learned by our fenfe of touch. 



V. Of Smell and of Tafte. 



THE objects of fmell are diflblved in the fluid 

 atmofphere, and thofe of tafte in the faliva, or other 

 aqueous fluid, for the better diffufing them on their 

 refpective organs, which feem to be" ftimulated into 

 animal motion perhaps by the chemical affinities of 

 thefe particles, which conftitute the fapidity and 

 ffclorofity of bodies with the nerves of fenfe, which 

 perceive them. 



Mr. Volta has lately obferved a curious circum- 

 fiance relative to our fenfe of tafte. If a bit of clean 

 lead and a bit of clean iilver be feparately applied to 

 the tongue and palate no tafte is perceived ; but by 

 applying them in contact in refpect to the parts out 

 of the mouth, and nearly fo in refpecl to the parts, 

 which are immediately applied to the tongue and 

 palate, a faline or acidulous tafte is perceived, as of 

 a fluid like a ft ream of electricity pafling from one 

 of them to the other- This new application of the 

 fenfe of tafte deferves further inveftigation, as it 

 may acquaint us with new properties of matter. 



From the experiments above mentioned of Gal- 

 vani, Volta, Fowler, and others, it appears, that 

 a plate of zinc and a plate of filver have greater 

 effect than lead and filver* If one edge of a plate 

 of filver about the fize of half a crown-piece be 

 placed upon the tongue, and one edge of a plate of 

 zinc about the fame fize beneath the tongue, and 



if 



