i64 THEPHILOSOPHY 



its weight. Thas, the air we breathe is perpetually impregnated 

 with an infinity of different particles which ftimulate the olfadory 

 nerves, and give rife to the fenfation of fmell. When our fenfes 

 are not vitiated by unnacural habits, they are not only faithful mo- 

 nitors of danger, but convey to us the moft excjuifite pleafures. 

 Even the fenfe of finelling is always productive either of pleafure 

 or pain. The fragrance of a rofe, and of many other flowers, is 

 not only pleafant, but gives a refrcfhing and delightful ftimulus to 

 the whole fyftem, and may be confidered as a fpecies of wholefome 

 nourifhment ; while the odours proceeding from hemlock, and from 

 many other noxious vegetable, animal, and mineral fubftances, arc 

 highly offenfive to our noftri's. Hence we are naturally compelled 

 to embrace the one clafs of fenfations and to avoid the other. 



Some animals, as the dng, the fox, the raven, 8cc. are endowed 

 with a moft exquifue fenfe of fmelling. A dog fcents various kinds 

 of game at confiderable diftances ; and, if the fad were not confirm- 

 ed by daily experience, it could hardly gain credit, that he can trace 

 the odour of his mafter's foot through all the winding ftreets of a po- 

 pulous city. If we judge from our own feelings, this extreme fen- 

 fibility in the nofe of a dog is to us perfedly incomprehenfible. 



The fenfe of finelling, like that of fome other fenfes, may be per- 

 verted or corrupted by habit. The fnuffing, chewing, and fmoking 

 tobacco, though at iirft difagreeable, become, by the power of habit, 

 not only pleafant, but almoll indifpenfible. The fame remark is ap- 

 plicable to the pradice of fwallowing ardent fpirits, the moft delete- 

 rious of all poifons, becaufe the moft extenfively employed. How 

 the natural ftate of the nerves, and of the fenfations conveyed by 

 them, fhould be fo completely changed, we are totally ignorant. 

 The conftitution of the nerves often varies in different individuals- 

 of the fame fpecies.- An odour which is difguftful to one man is 



lughly 



