may say indeed, that taste and smell are so nearly allied to each other, that, if one be performed by vibrations, the other must also. I will repeat two principal observations.
First, If the varieties of kind in vibrations be combined with those of degree, we shall have a large fund for explaining the various fragrant and fœtid smells, notwithstanding that the first always agree in falling short of the solution of continuity, the last in going beyond it.
Secondly, the differences of kind in smells are not so many as may appear at first sight, a difference in degree often putting on the appearance of one in kind. Thus an onion cut fresh, and held close to the nose, smells very like asafœtida; and asafœtida, in an evanescent degree, like onion or garlick. Thus a dunghill at a distance has smelt like musk, and a dead dog like elder-flowers. And fœtids are said to enhance the flavour of fragrants. The three last instances shew, that pleasure and pain are very nearly allied to one another in this sense also.
It will be evident, upon a moderate attention, that the grateful smells, with which natural productions abound, have a great share in enlivening many of our ideas, and in the generation of our intellectual pleasures; which holds particularly in respect of those that arise from the view of rural objects and scenes, and from the representations of them by poetry and painting. This source of these pleasures may not indeed be easy to be traced up in all the particular cases; but that it is a source, follows necessarily from the power of association.
In like manner, the mental uneasiness, which attends shame, ideas of indecency, &c. arises, in a considerable degree, from the offensive smells of the excrementitious discharges of animal bodies. And it is remarkable in this view, that the pudenda are situated near the passages of the urine and fæces, the two most offensive of our excrements.
We may suppose the intellectual pleasures and pains, which are deducible from the flavours, grateful and ungrateful, that ascend behind the uvula into the nose during mastication, and just after deglutition, to have been considered in the last section under the head of taste, since these flavours are always esteemed a part of the tastes of aliments and medicines. And indeed the olfactory nerves seem to have as great a share in conveying to us both the original and derivative pleasures, which are referred to the taste, as the nerves of the tongue; which may help us to account for the largeness of those nerves in men, to whom smell, properly so called, is of far less consequence than any other of
