us to become aware of the existence of some external circumstance. If these currents did not carry with them some sort of sympathy, then there would be no such perception. We must not therefore think that it is the air which receives a certain form, under the action of the voice or of some other sound. For it is utterly impossible that the voice should act in this manner on the air. But the percussion produced in us when we, by the utterance of a voice, cause a disengagement of certain particles, constitutes a current resembling a light whisper, and prepares an acoustic feeling for us.
“We must admit that the case of smelling is the same as that of hearing. There would be no sense of smell if there did not emanate from most objects certain particles capable of producing an impression on the smell. One class being ill-suited to the organ, and consequently producing a disordered state of it, the other being suited to it, and causing it no distress.
“One must also allow, that the atoms possess no one of the qualities of sensible objects, except form, weight, magnitude and anything else is unavoidably inherent in form; in fact, every quality is changeable, but the atoms are necessarily unchangeable; for it is impossible but that in the dissolution of combined bodies, there must be something which continues solid and indestructible, of such a kind, that it will not change either into what does not exist, or out of what does not exist; but that it results either from a simple displacement of parts, which is the most usual case, or from the addition or subtraction of certain particles. It follows from that, that that which does not admit of any change in itself, is imperishable, participates in no respect in the nature of changeable things, and in a word, has its dimensions and forms immutably determined. And this is proved plainly enough, because even in the transformations which take place under our eyes, in consequence of the retrenchment of