In examining, then, according to their organs, our classes of sensation; and considering what feelings the organic affections excite _at present_, and what we may suppose them to have excited _originally_,--I shall begin with those which are most simple, taking them in the order of smell, taste, hearing,--not so much, from any hope, that the information, which these afford will throw any great light on the more complex phenomena of sight and touch, as because the consideration of them is easier, and may prepare you gradually for this difficult analysis, which awaits us afterwards, in the examination of those more perplexing phenomena. I begin, then, with the consideration of that very simple order of our sensations which we ascribe to our organ of SMELL. The organ of smell, as you well know, is principally in the nostrils,--and partly also in some continuous cavities on which a portion of the olfactory nerves is diffused. Naribus interea consedit odora hominum vis Docta leves captare auras, Panchaia quales Vere novo exhalat, Floræve quod oscula fragrant Roscida, cum Zephyri furtim sub vesperis hora Respondet votis, mollemque aspirat amorem.[74] When the particles of odour affect our nerves of smell, a certain state of mind is produced, varying with the nature of the odoriferous body. The mere existence of this state, is all the information which we could originally have received from it, if it had been excited previously to our sensations of a different class. But, with our present knowledge, it seems immediately to communicate to us much more important information. We are not merely sensible of the particular feeling, but we refer it, in the instant,--almost in the same manner, as if the reference itself were involved in the sensation,--to a rose, hemlock, honeysuckle, or any other substance, agreeable or disagreeable; the immediate presence, or vicinity of which we have formerly found to be attended with this particular sensation. The power of making the reference, however, is unquestionably derived from a source different from that, from which the mere sensation is immediately derived. We must previously have seen, or handled, the rose, the hemlock, the honeysuckle; or if, without making this particular reference, we merely consider our sensation of smell as caused by some unknown object external to our mind, we must at least have previously seen or handled some other bodies, which excited, at the same time, sensations analogous to the present. If we had been endowed with the sense of smell, and with no other sense whatever, the sensations of this class would have been simple feelings of pleasure or pain, which we should as little have ascribed to an external cause, as any of our spontaneous feelings of joy or sorrow, that are equally lasting or equally transient. Even at present, after the connexion of our sensations of a fragrance with the bodies which we term fragrant, has been, in a great