not to be susceptible of division. And to that small particle must belong not only divisibility, but the qualities of solidity, extension, and figure.

§. 54. Of the secondary qualities of matter.

The SECONDARY qualities of bodies are of two kinds; (1) Those, which have relation to the perceiving and sentient mind; (2) Those, which have relation to other bodies.

Under the first class are to be included sound, color, taste, smell, hardness and softness, heat and cold, roughness and smoothness, &c. When we say of a body it has sound, we imply in this remark, that it possesses qualities, which will cause certain effects in the mind; the term sound being applicable by the use of language both to the qualities of the external object, and to the effect produced within. When we say it has color, we always make a like reference to the mind, which beholds and contemplates it; and it is the same of the other secondary qualities of this description.

The other class of secondary qualities, (or properties as they are not unfrequently termed,) those which have relation to other material bodies, are exceedingly various and numerous. The material substance, which in relation to the mind possesses the qualities of sound and color, may possess also in relation to other bodies the qualities or properties of malleability, fusibility, solubility, permeability, and the like.

§. 55. Of the nature of mental powers or faculties.

We have spoken of Perception as a POWER of the mind, as well as a mental state or act. This two-fold use of the term is owing to the imperfection of language. The same term, at least in the English language, signifies both the result, and the corresponding power; and oftentimes there is nothing but the connection to determine which is meant. But we have recurred to this subject here, merely for the purpose of suggesting the importance of keeping in recollection, that mental powers, (what are otherwise called faculties and not unfrequently susceptibilities,) are not distinct from the mind itself. They are only the ability of the mind to act in a particular way. We apply the term also in other cases; we speak of the power or faculty of the MEMORY, of REASONING,

of IMAGINATION, &c. Such expressions are found in all languages, and cannot well be avoided. They are brief, and, on the whole, convenient representations of the various ways, in which the soul is capable of acting, or exerting itself.

But while we keep in recollection, that powers or faculties are only the ability of the mind to act in a particular way, it is further to be noticed, that in many cases what are so called are complex in their nature; they are made up in their results of various simple feelings, and imply the exercise of more than one simple susceptibility. It is proper, therefore, to analyze them, and to become acquainted with their parts; otherwise our notions will be confused, and often erroneous. Still we cannot wholly lay aside the expressions, which use and the wants of men have introduced; nor is this necessary, if we will but take the pains to explain the true nature of the operations, and of that ability of the mind, which they profess to represent. If philosophers should undertake to introduce a whole new system of terms, (and the credit is due to Kant that there is not wanting a notable instance of this in modern times,) still it would be necessary to employ the old ones, in order to make them understood by mankind generally. As a general rule it is better to employ the common and acknowledged phraseology, only taking care to limit and explain it so far as it may be liable to misapprehension in consequence of a new and scientific application. "It looks too much like affectation, (says Locke, speaking of these forms of speech,) wholly to lay them by; and philosophy itself, though it likes not a gaudy dress, yet when it appears in public, must have so much complacency, as to be clothed in the ordinary fashion and language of the country, so far as it can consist with truth and perspicuity."

CHAPTER THIRD.

THE SENSES OF SMELL AND TASTE.

§. 56. Nature and importance of the senses as a source of knowledge.

It is desirable to keep clearly in the mind the precise relation of the senses to the origin, progress, and amount of our knowledge, and to possess if possible a correct understanding of their true value. In a certain sense the possession of the bodily organs, with which we are furnished, is not essential and pre-requisite to the possession of that knowledge, which we are accustomed to ascribe to them. There is nothing unwarrantable and unreasonable in the supposition, that the knowledge, which we now have by their means, might have been possessed without their aid, either immediately, or in some way altogether different. Their use and indispensableness in the acquisition of a certain portion of what men are permitted to know, is a matter of arrangement and appointment on the part of our Maker, It is undoubtedly an evidence of the correctness of this remark, that the Supreme Being has a full acquaintance with all those outward objects, which present themselves to our notice, without being indebted to any material instrumentality and mediation. He perceives in another way, or rather all knowledge is inherent in, and originally and unalterably essential to himself.

other

It is not so, as we have reason to believe, with any beings, and certainly not with man. Although a great part of his knowledge relates to material things, he is so formed, and his constitution is so ordered, that he is wholly dependent for it on the senses.-Deprive him of the ear, and all na

THE SENSES OF SMELL AND TASTE.

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ture becomes voiceless and silent; deprive him of the eye, and the sun and moon withdraw their light, and the universe becomes darkened like sackcloth; deprive him of the sense of touch, and he is then entirely insulated, and as much cut off from all communication with others, as if he were the only being in existence.

§. 57. Of the connection of the brain with sensation and perception.

It may perhaps be asked, Whether these views are intended to exclude the brain, as having a connection with the senses in the results, which are here ascribed to them? And this inquiry leads us to observe, (what has been before alluded to,) that the brain is a prominent organ in the material part of the process of sensation and of external perception. The senses evidently cannot be separated from the nervous system. But the substance, which is found in the nerves, excepting the coat in which it is enveloped, is the same as in the brain, being of the same soft and fibrous texture, and in continuity with it. As a general statement, when the brain has been in any way injured, the inward sensation, which would otherwise be distinct on the presentation of an external body, is imperfect. Also if the nerve be injured, or if its continuity be disturbed by the pressure of a tight ligature, the effect is the same; a circumstance which goes to confirm the alleged identity of substance in the two.

The brain, therefore, and whatever of the same substance is in continuity with it, particularly the nerves, constitute the sensorial organ, which, in the subordinate organs of taste, smell, sight, touch, and hearing, presents itself under different modifications to external objects. On this organ, the sensorial, as thus explained, an impression must be made, before there can be sensation and perception.

An impression, for instance, is made on that part of the sensorial organ called the auditory nerve, and a state of mind immediately succeeds, which is variously termed, according to the view in which it is contemplated, either the sensation, or the perception of sound. An impression is made by the rays of light on that expansion of the optic nerve, which forms what is called the RETINA of the eye, and the intellectual principle is immediately brought into that new position, which

is termed visual perception or a perception of sight. The hand is impressed on a body of an uneven and rough surface, and immediately consequent on this application and pressure, is that state of mind, which is termed a sensation or perception of roughness.

§. 58. Order in which the senses are to be considered.

In considering those ideas, which we become possessed of by means of the senses, it is natural to begin with that sense, which will cause us the least difficulty in the analysis of its results, and to proceed to others successively, as we find them increasing in importance. It may not be altogether easy to apply this principle with strictness, but it will answer all the purpose, for which it is here introduced, if we consider the senses in the following order, the smell, taste, hearing, touch, and sight.

The mind holds a communication with the material world by means of the sense of smelling. All animal and vegetable bodies, (and the same will probably hold good of other bodies, though generally in a less degree,) are continually sending out effluvia of great subtility. These small particles are rapidly and widely scattered abroad in the neighborhood of the body from which they proceed. No percipient being can come within the circumference occupied by these continually moving and volatile atoms, without experiencing effects from it.

§. 59. Of the sense and sensation of smell.

The medium, through which we have the sensations and perceptions of smell, is the organ, which is termed the olfactory nerve, situated principally in the nostrils, but partly in some continuous cavities. When any odoriferous particles, sent from external objects, affect this organ, there is a certain state of mind produced, which varies with the nature of the odoriferous bodies. But we can no more infer from the sensation itself merely, that there exists any necessary connection between the smell and the external objects, than that there exists a connection between the emotions of joy and sorrow and the same objects. It might indeed be suggested to us by the change in our mental states, that there must be some cause or antecedent to the change, but this suggestion