Page images
PDF
EPUB

CHAP.

tion in poetry* ; but that is upon another prin Of Hearing. ciple, which will be hereafter examined.

IV.

16. It has been already observed that all sensation is really produced by contact; the effluvia, that we smell, and the vibrations, that we hear, being locally and essentially in the nose and the ears, just as the food, which we taste, is in the mouth, or the implements that we hold, are in the hands. The mere sense of hearing, therefore, can afford us no information concerning the distance or direction of a sonorous object, which can only be perceived by a faculty acquired entirely by habit; though, by being habitual, the exercise of it has become as spontaneous and instantaneous, as that of any natural or organic faculty belonging to our constitutions. If this needed any proof, and was not clearly demonstrated by the formation of the organs, the common trick of a ventriloquist, who can make the sound of his voice appear to come in any direction, or from any distance within the reach of its being heard, would be fully sufficient: for this effect is produced merely by modifying it, as it would be modified to the ear, if it had really come in that direction, or from that distance. We, therefore, judge of the directions of sounds,

Nihil intrare potest in affectum, quod in aure, velut quodam vestibulo, statim offendit. Quintil. Inst. 1. ix *. iv.

[ocr errors]

and the distances of their causes, solely by certain modes of the vibrations affecting the organ, which usually distinguish each respectively, and which are accordingly associated with them in the mind; but which may, nevertheless, be produced by other means so perfectly as to work an entire deception even in the most acute observers.

17. This is an extremely important consideration in enabling us to estimate properly the grandeur or sublimity of sound; which can no otherwise arise from its loudness, than as that loudness excites an idea of power in the sonorous object, or in some other associated with it in the mind: for a child's drum close to the ear fills it with more real noise, than the discharge of a cannon a mile off; and the rattling of a carriage in the street, when faintly and indistinctly heard, has often been mistaken for thunder at a distance. Yet no one ever imagined the beating of a child's drum, or the rattling of a carriage over stones, to be grand or sublime; which, nevertheless, they must be, if grandeur or sublimity belong at all to the sensation of loudness. But artillery and lightning are powerful engines of destruction; and with their power we sympathize, whenever the sound of them excites any sentiments of sublimity; which is only when we apprehend no danger from them; or at least no degree of

• СНАР.

IV.

Of Hearing.

СНАР.

IV.

Of Hearing.

danger sufficient to impress fear: for so far is terror from being a source of the sublime, that the smallest degree of fear instantly annihilates it, as far as relates to the person frightened; and to that person only is the object terrible. To all others it is merely powerful, or capable of inspiring terror to those who are more susceptible of it. But of this more shall be said in the proper place.

CHAPTER V.

OF SIGHT.

1. SIGHT, as well as hearing, is produced by immediate contact of the exciting cause with the organ; which exciting cause is the light reflected, from the objects seen, upon the retina of the eye; the pictures upon which, by some impressions or irritations upon the optic nerves, the modes of which muft be for ever unknown to us, are conveyed to the mind, and produce the sense of vision, the most valuable of all our senses.

2. The sensation, therefore, felt upon opening the eyes for the first time, must necessarily be that of the objects seen touching them; as it proved to be in the case of the boy, who, at the age of fourteen or thereabouts, obtained his sight, after having been blind from his birth, by an operation performed upon his eyes by Cheselden. For a considerable time, and till the sense of seeing had been aided and corrected by that of touch, all the objects seen appeared only as variations of light acting upon the eye for the colours of objects are only different rays of light variously reflected from their surfaces *; and their visible pro

See Newton's Theory of Light and Colours.

CHAP.
V.

Of Sight.

CHAP.
V.

Of Sight.

jection is merely gradation and opposition of light and shadow; which, in round and undulating bodies, are intermixed gradually; and, in those of angular forms, abruptly. It is, therefore, only by habit and experience that we form analogies between the perceptions of vision and those of touch, and thus learn to discover projection by the eye; for, naturally, the eye sees only superficial dimension; as clearly appears in painting and all other optical deceptions, which produce the appearance of projection or thickness upon a flat surface. The faculty, however, when acquired, as it is in all adult persons who have seen from their birth, is exercised as readily and instantaneously as any natural faculty whatsoever *.

s. The perception of visible projection being thus artificial, that of visible distance mustnecessarily be so likewise: for distance is only projection extended. Accordingly we find that our improved perception of visible distance extends no further than that experience, by which it has been formed and improved: for of the immense distances of the heavenly bodies from each other, and from the earth, we discover nothing by looking at them; they all appearing to occupy the surface of one

* See Dr. Reid's Essay on the Mind, where a very clear and full explanation of the theory of vision is given.

« PreviousContinue »