from that of smell by the last’s being extended upon bones; so as to be much more sensible and irritable upon that account. To which we may add, that as a watery fluid is the proper menstruum for the dissolution of sapid particles, and conveyance of their tastes, so smells seem to make their impressions by means of air-particles.
Here we may observe, first, that since the smells of bodies diffuse themselves in general to great distances, and in some cases to immense ones, the odoriferous particles must repel each other; and consequently be easily susceptible of vibratory motions, for the same reasons as the particles of common air, or those of the æther. We may even suppose, that odoriferous particles are thrown off by vibratory motions in the body that emits them.
May not, however, the odoriferous particles be attracted by the body which emits them, after they have receded from it to a certain distance, and so follow it, in some measure, like an atmosphere? It is hard to account for the small or no diminution of weight in odoriferous bodies, after they have continued to emit smells for a long time, but upon some such supposition.
Secondly, Heat, friction, and effervescence, are all very apt to excite and increase smells; and have all a connexion with vibratory motions in the judgment of most philosophers.
Thirdly, Since heat and friction excite and increase smells, these may have some connexion with electricity; which is supposed by many philosophers to depend upon vibratory motions. And as air-particles are electrics per se, they may have, on this account, a peculiar fitness for conveying and impressing smells. May not air-particles, and odoriferous ones, repel each other?
Fourthly, It is usual, when we desire to receive a smell in full strength and perfection, to make quick, short, alternate inspirations and expirations. This corresponds to the rubbing the ends of the fingers upon the body to be examined by feeling, and the tongue against the palate in tasting. And all these three actions appear to be some presumption in favour of the doctrine of vibrations.
Fifthly, The greatness and quickness of the effect of odours upon the whole nervous system seem very suitable to the doctrine of vibrations. For this must be owing to the mere impression of some motion, there not being time for the absorption of particles sufficient for the effect produced. When sweet smells cause a sudden faintness, and deliquium animi, they may perhaps agitate the whole system of small medullary particles so much, as to make them attract each other with sufficient force to stop all vibratory motions; just as has been observed of the particles of muscular and membranous fibres. And the smells
