Is the rose fragrant? The sense of smell is indeed only a continuation of that of taste. In smelling, the nerves are touched by only infinitesimally small particles of the substances reaching them, and are only able to receive an impression from this excessive distribution. This is also true of taste, to a certain degree, as it is impossible to fully perceive a flavor until the substance is tolerably comminuted, as we smack our lips to obtain it. Indeed, it may be questioned whether the whole of taste may not lie in the capabilities of different substances for great subdivision of particles. If quartz could be made to dissolve into excessively minute particles as readily as sugar, it might have its own special flavor. Some odors are offensive in dense quantities which are highly agreeable when wafted to us in delicate atoms,—musk, for instance. The rose secretes a volatile oil, the wonderfully small atoms of which, on touching the nerves of smell, communicate a peculiar sensation. This odor, like the sweetness, exists only in the nerves affected; and a trifling disaffection of the nerves suffices to destroy it entirely. The chemist can also analyze the oil, but he does not enumerate in its elements odor. In fact, we have no words to express the sensation of smell. We say sweet, sour, bitter; but have no terms to express the differing sensations produced on us by the rose, lily, violet, and pink. Their oily atoms awaken different sensations in the delicate nerves they touch. The sensation awakened may be due to chemical action induced by them in the system. But whether chemical or physical, the result of their touch is a motion of matter, an impulse communicated to the brain, the sensation of the organ being—the reception of this initiative force being—what we designate as odor. The fragrance of the rose lies, then, in the contractions of special nerves, which thus respond to the touch of the oily particles that are blown against them.
Does the trumpet sound? A vibration of matter causes the surrounding air to vibrate in consonance with it; and the waves of air thus created, breaking against the auditory nerve, awaken a peculiar sensation which we call sound. The trumpet, vibrating variously, as the valves are moved and the air forced through it, initiates waves of air of different lengths; and as they are communicated to the surrounding air with amazing rapidity, they successively strike the listener's ear. As the waves of light touch the optic nerve, so do the grosser waves of air touch the auditory nerve. But sound is only a recognized sensation when the waves of air are within a certain measurement, a maximum and minimum of length. The rush of a whirlwind has no sound, except when arrested by some object, and smaller waves of the vast billows of rolling air are created. We say that the wind roars. But the tremendous currents above us, which sweep along the vast masses of vapor, are noiseless until they touch the earth, and some little trifling eddies are made in their lower sweep by hills and trees and houses. It is then only noise. The ear requires yet smaller waves of air to experience the sensation of tone. The lowest note of a piano has barely enough of it to give a definite idea. As the waves become shorter, the ear begins to be pleasantly affected, and the realm of music is reached. Within a certain restricted length of air-waves lies all of the pleasurable sensation which we call musical tone. But as we rise in the scale the tone begins to become uncertain, until the highest note of the instrument is again indefinite noise. The attenuated tone-waves of Nature are also inappreciable by the auditory nerves, and an obscure hum or buzz is all that can be perceived, until, finally, the eye detects motion which the ear utterly fails to perceive as sound. The results of the air-waves are appreciable by sight and feeling; but the waves which are heard are not those which create the disturbance in nature we see and feel. The wild gust which seizes a tree and bows it to the earth is only heard when the branches it sways, or the leaves which it rustles, give out a secondary and far more attenuate series of waves. A locust, on a warm, sunny day, will agitate the air around him with a series of waves which affect the ear far more powerfully than the wind which sighs in the waving trees above him. Thus sound is the answering sensation of the auditory nerve to the touch of air-waves; and these waves must be within certain circumscribed limits of magnitude to awaken that sensation at all. The greater or less violence with which they strike the ear causes them to appear loud or soft. We can imagine a development of the nerves, or of the ear apparatus, which might allow them to be influenced by waves of greater volume and less rapid flow, and also by those of diminished size and accelerated movement The trumpet then does not sounds the ear sounds, and in the ear alone lies the music that it makes. The deaf man, whose auditory nerves are not sensitive to air-waves, sees the clouds move and the trees sway, the brook ripple and the trumpeter with his tube at his lips; but the air-waves they all create pass by him, and sound is inconceivable. That sound is a mere nervous sensation is further proved by the fact that we have disturbances of the auditory nerve which we call singing in the ears. No waves of air create this disagreeable music. It arises from some affection of the nerve, which irritates it to a vibration similar to that which it undergoes when air-waves of a certain intensity reach it.
We say the sound rolled on, the odor was wafted, the color was printed, our language and our thoughts implying that the sound, the odor, the color, are things, when in reality they are all mere sensations, answering to the touch of physical agents. All sensation is nerve-motion. Outer stimulus, applied to the nerves, causes contractions which, communicating with the brain, give the idea of color or taste or sound.
The sense of feeling is a recognition of the existence of objects by a duller perception than the others, though all of the senses attain their perceptions by feeling, in the strict meaning of the word. We say things feel hard or soft, the varying density of the objects being the cause of the varying sensations they awaken. Smoothness and roughness are varying outlines of surface, existing as physical conformation; the pleasurable or disagreeable sensations awakened in us by contact being due to the greater or less irritation of the nerves of feeling that attrition with it occasions. Motion is absolutely necessary to give us an ides of the density or configuration of an object. The mere touch of that object is insufficient to possess us with its nature. Iron and down are indistinguishable, unless we, to a certain extent, manipulate them. Glass would be indistinguishable from sand-paper did we not to a certain extent pass our fingers over the different surfaces. Mere touch would not suffice. We have the evidence of all of our senses to prove to us the nature of an object. It tastes or smells or vibrates or is colored; the varied sensations thus awakened combining to give us our totality of conception. The rose reflects light-waves which the eye feels red; it emits oil-particles which the nose feels fragrant; it touches our tongue, and feels pleasantly; it touches our fingers, and feels soft and smooth. It exists in nature as a physical structure, and its existence is evident to us through the various sensations it creates in different nerves of our bodies, and through them alone.
One of the ancient philosophies maintained that all Nature is but the phantasm of our senses. Had it, after first granting that the senses themselves were evidences of matter and motion, maintained that Nature was only evident to us through them, it would have been simple truth. Our perceptions of Nature are limited to the capacity of our nervous structure. We frequently make the mistake of endowing matter with attributes which it does not possess, and which are resident only in the impression communicated to us by forces emanating from it, the forces being we know not what. And we can understand that there may be forces in nature as powerful as those which we perceive by our senses, but which are utterly unrecognized by them. We can understand that it were possible for organized beings to possess fifty instead of five senses, which might receive from nature other impressions and awaken other emotions as beautiful and as beneficent as those arising from sight and hearing.
SONNET.
Rather, my people, let thy youths parade
Their woolly flocks before the rising sun;
With curds and oat-cakes, when their work is done,
By frugal handmaids let the board be laid;
Let them refresh their vigor in the shade,
Or deem their straw as down to lie upon,
Ere the great nation which our sires begun
Be rent asunder by hell's minion, Trade!
If jarring interests and the greed of gold,
The corn-rick's envy of the minéd hill,
The steamer's grudge against the spindle's skill,—
If things so mean our country's fate can mould,
O, let me hear again the shepherds trill
Their reedy music to the drowsing fold!