Odour, is that property of bodies by which they affect the sense of smell at a distance, whether in a pleasant or disagreeable manner.
It has been ascertained by numberless observations, that every species of animals, as well as of diseases, emits a peculiar odour; which, however, can be distinguished only by the most refined sense. The American Indians are able to ascertain, by smell, the proximity, or distance, of their enemies ; and whether they: are white men or black. Anatomists have lately discovered, that this astonishing acuteness of smelling must be attributed to the uncommon size of the nostrils, which are much dilated among these nations. The faculty of distinguishing odours, doubtless has. great influence upon the rnorals and on the disposition of the mind ; hence Rousseau justly terms it " the sense of ima gination." Virey, a modern French writer, has devoted a particular treatise to the inquiry into the great etfect of this sense, on the passion of love; and, in another paper, he examines the odours exhaled by living animals. - The celebrated Monk of Prague, was a remarkable instance of having pre-ed all the vigour and natural extent of his sense of smelling in the midst of society: thus, it is said, he could not only distinguish every person, but even ascertain the respective purity of female manners ; and it is much to be re-gretted, that death prevented him from finishing a Treatise on Odours. Having already, on different occasions, stated the effects of strong -. ly odoriferous substances on the human body, we shall in this place communicate an observation which may, perhaps, at some future period, be applied to very useful purposes in the healing art. M. Pre-vost, an ingenious Frenchman, has lately discovered a method of rendering the exhalations of odorous bodies visihle. This remarkable phenomenon was re-produced before the National Institute at Paris, by various experiments, that are equally simple and striking.—A few drops of water are to be distributed at equal distances from each other, on the surface of a glazed plate, or looking glass.— Next, the odorous substance, for instance, a piece, of camphor, is placed in the middle.: among other effects, the water immediately retreats to a considerable distance, in a circle, from the exhaling body, so that the intermediate space becomes perfectly -dry. In proporQ 1 L tion to the strength of the smell, this interval will be more or less considerable, and thus serve as a measure or scale for ascertaining the intensity of the odour.