SOUND, or Manion, sense of. The sense of sight is effected by rays of light, proceeding from the different objects to the retina. The sense of feeling is effect ed by the contact of its various objects with the body, or by the vigorous or un sound state of the parts of the body. The sense of taste is affected by certain par ticles of substances which are dissolved by the saliva, and thus brought into con tact with the organs of taste. The sense of smell is affected by particles which va rious substances arc continually sending into the air, and which impress the mem brane which lines the cavity and bones of the nose. The sense of hearing is aflect ed by the pulsations or vibrations of the air, which are caused by its own expan sion, or by the vibrations of sounding bo dies. These sensations, or vibrations in the air, are called sounds, as are also the sensations which they produce. The or gat' of hearing is much more complica ted and much less understood, than that of sight. We shall here give a very ge neral account of it, and refer those who wish for further information to the article AaATOMT. The external ear collects and modifies sounds; and by a long chan nel communicates them to the internal ear : this consists, in the first place, of what is called the drum of the ear, which is a small cavity, closed towards the open ing of the ear by a delicate membrane. In the drum are three or four very small bones, furnished with muscles and joints. From the drum are several openings, one of which is to the mouth ; the others com municate into the different recesses of the ear. One of these leads into the labyrinth, which consists, first, of a small irregular cavity, next of three semi-circular canals, and lastly of a winding spiral canal, not unlike sonic sea shells. All these parts of the cavity are lined with a very delicate membrane, and filled with a watery fluid, which conveys to the portions of the nerve in contact with it, the vibrations received from the membrane which separates the labyrinth from the drum of the ear. The vibrations of the air act upon the drum, and thus set in motion the series of small bones in the cavity of the drum ; these communifate the vibrations to the mem brane which separates the drum from the labyrinth, and this (as before mentioned) produces vibrations in the watery fluid, in the several parts of the labyrinth, and conveys to the nervous branches, which line the labyrinth, the vibrations original ly produced on the drum. The mecha
nism is complicated, but what we under stand must increase our reverential admi ration of the skill which produced it.
There are colours which of themselves, without associated ideas, are agreeable to the sight ; so it is reasonable to believe, that there are sounds which of them. selves, without associated deal, are agree able to the ear. This is authorized also by direct experience. All moderate and tolerably uniform sounds please young children ; and during the whole of life, various combined and simple sounds give pleasure to the mind, without any refer ence to the associated ideas. Hence it appears that the pleasures of hearing aid considerably in the formation, or at least in the increase, of the mental plea sures : indeed in connection with those of sight, they constitute nearly the whole of the pleasures of sublimity and beauty.
It is a well known fact, that the ideas left by the sensations of sight arc the most vivid and distinct of any : next to these are those produced by the sensa tion of hearing. Few can form a distinct, certainly not a vivid, conception of the feel of any sebstance, which has present ed sensations through the medium of the touch, and not many more can of a taste, or of a smell, though thinking of parti cular taste produces considerable effu sion of the saliva. Of objects of the sight we are able to form conceptions, which often approach in vividness and distinct ness to the original sensations, and which sometimes overpower those actually pre sent in the mind, so as in many cases to lead to the belief of a real object, and consequently to lead to the belief of appa ritions, &c. Few, we believe, possess the power of forming conceptions of sounds nearly equal in vividness and distinctness with the original sensation ; but they are frequently perceptible. After we have heard music, or conversed much with a person, trains of audible ideas frequently pass in the mind. So, when we arc thinking or reading slowly and carefully, we can Generally trace the relics of the audible impressions of the words suggest ed by the thoughts, or the sight of the letters ; that is, we have faint conceptions of the sounds of these words.