would rarely, if ever, lead us to a wrong choice of food among the productions of nature; although the artificial compositions of a refined and luxurious cookery, or of chemistry and pharmacy, may often impose upon both, and produce things agreeable to the taste and smell, which are noxious to health. And it is probable that both smell and taste are vitiated, and rendered less fit to perform their natural offices, by the unnatural kind of life men commonly lead in society.

These senses are likewise of great use to distinguish bodies that cannot be distinguished by our other senses, and to discern the changes which the same body undergoes, which, in many cases, are sooner perceived by taste and smell than by any other means. How many things are there in the market, the eating-house, and the tavern, as well as in the apothecary and chemist's shops, which are known to be what they are given out to be, and are perceived to be good or bad in their kind, only by taste or smell? And how far our judgment of things, by means of our senses, might be improved by accurate attention to the small differences of taste and smell, and other sensible qualities, is not easy to determine. Sir Isaac Newton, by a noble effort of his great genius, attempted, from the colour of opaque bodies, to discover the magnitude of the minute pellucid parts of which they are compounded: and who knows what new lights natural philosophy may yet receive from other secondary qualities duly examined?

Some tastes and smells stimulate the nerves and raise the spirits: but such an artificial elevation of the spirits is, by the laws of nature, followed by a depression, which can only be relieved by time, or by the repeated use of the like stimulus. By the use of such things we create an appetite for them, which very much resembles, and hath all the force of a natural one. It is in this manner that men acquire an appetite for snuff, tobacco, strong liquors, laudanum, and the like.

Nature, indeed, seems studiously to have set bounds to the pleasures and pains we have by these two senses, and to have confined them within very narrow limits, that we might not place any part of our happiness in them; there being hardly any smell or taste so disagreeable that use will not make it tolerable, and at last perhaps agreeable, nor any so agreeable as not to lose its relish by constant use. Neither is there any pleasure or pain of these senses which is not introduced or followed by some degree of its contrary, which nearly balances it; so that we may here apply the beautiful allegory of the divine Socrates-that, although pleasure and pain are contrary in their nature, and their faces look different ways, yet Jupiter hath tied them so together that he that lays hold of the one draws the other along with it.

As there is a great variety of smells, seemingly simple and uncompounded, not only altogether unlike, but some of them contrary to others, and as the same thing may be said of tastes, it would seem that one taste is not less different from another than it is from a smell: and therefore it may be a question, how all smells come to be considered as one genus, and all tastes as another? What is the generical distinction? Is it only that the nose is the organ of the one and the palate of the other? or, abstracting from the organ, is there not in the sensations themselves something common to smells, and something else common to tastes, whereby the one is distinguished from the other? It seems most probable that the latter is the case; and that, under the appearance of the greatest simplicity, there is still in these sensations something of composition.

If one considers the matter abstractly, it would seem that a number of sensations, or, indeed, of any other individual things, which are perfectly simple and uncompounded, are incapable of being reduced into genera and species; because individuals which belong to a species must have something peculiar to each, by which they

are distinguished, and something common to the whole species. And the same may be said of species which belong to one genus. And, whether this does not imply some kind of composition, we shall leave to metaphysicians to determine.

The sensations both of smell and taste do undoubtedly admit of an immense variety of modifications, which no language can express. If a man was to examine five hundred different wines, he would hardly find two of them that had precisely the same taste. The same thing holds in cheese, and in many other things. Yet, of five hundred different tastes in cheese or wine, we can hardly describe twenty, so as to give a distinct notion of them to one who had not tasted them.

Dr. Nehemiah Grew, a most judicious and laborious naturalist, in a discourse read before the Royal Society, anno 1675, hath endeavoured to shew that there are at least sixteen different simple tastes, which he enumerates. How many compounded ones may be made out of all the various combinations of two, three, four, or more of these simple ones, they who are acquainted with the theory of combinations will easily perceive. All these have various degrees of intenseness and weakness. Many of them have other varieties; in some the taste is more quickly perceived upon the application of the sapid body, in others more slowly-in some the sensation is more permanent, in others more transient-in some it seems to undulate or return after certain intervals, in others it is constant; the various parts of the organ-as the lips, the tip of the tongue, the root of the tongue, the fauces, the uvula, and the throat-are some of them. chiefly affected by one sapid body, and others by another. All these, and other varieties of tastes, that accurate writer illustrates by a number of examples. Nor is it to be doubted, but smells, if examined with the same accuracy, would appear to have as great variety.

CHAPTER IV.

OF HEARING.

Section I.

VARIETY OF SOUNDS-THEIR PLACE AND DISTANCE LEARNED BY CUSTOM, WITHOUT REASONING.

SOUNDS have probably no less variety of modifications, than either tastes or odours. For, first, sounds differ in tone. The ear is capable of perceiving four or five hundred variations of tone in sound, and probably as many different degrees of strength; by combining these, we have above twenty thousand simple sounds that differ either in tone or strength, supposing every tone to be perfect. But it is to be observed, that to make a perfect tone, a great many undulations of elastic air are required, which must all be of equal duration and extent, and follow one another with perfect regularity; and each undulation must be made up of the advance and recoil of innumerable particles of elastic air, whose motions are all uniform in direction, force, and time. Hence we may easily conceive a prodigious variety in the same tone, arising from irregularities of it, occasioned by the constitution, figure, situation, or manner of striking the sonorous body; from the constitution of the elastic medium, or its being disturbed by other motions; and from the constitution of the ear itself, upon which the impression is made.

A flute, a violin, a hautboy, and a French horn, may all sound the same tone and be easily distinguishable. Nay, if twenty human voices sound the same note, and with equal strength, there will still be some difference.

The same voice, while it retains its proper distinctions, may yet be varied many ways, by sickness or health, youth or age, leanness or fatness, good or bad humour. The same words spoken by foreigners and natives—nay, by persons of different provinces of the same nationmay be distinguished.

Such an immense variety of sensations of smell, taste, and sound, surely was not given us in vain. They are signs by which we know and distinguish things without us; and it was fit that the variety of the signs should, in some degree, correspond with the variety of the things. signified by them.

It seems to be by custom that we learn to distinguish both the place of things, and their nature, by means of their sound. That such a noise is in the street, such another in the room above me; that this is a knock at my door, that a person walking up stairs-is probably learnt by experience. I remember, that once lying abed, and having been put into a fright, I heard my own heart beat; but I took it to be one knocking at the door, and arose and opened the door oftener than once, before I discovered that the sound was in my own breast. It is probable, that, previous to all experience, we should as little know whether a sound came from the right or left, from above or below, from a great or a small distance, as we should know whether it was the sound of a drum, or a bell, or a cart. Nature is frugal in her operations, and will not be at the expense of a particular instinct, to give us that knowledge which experience will soon produce, by means of a general principle of human

nature.

For a little experience, by the constitution of human nature, ties together, not only in our imagination, but in our belief, those things which were in their nature unconnected. When I hear a certain sound, I conclude immediately, without reasoning, that a coach passes by. There are no premises from which this conclusion is in