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Show 78 SIGHT AND IIEARINO. nature, and the other to learn from our fellow-m~n, and yet the two work beautifully together for our _mstruc1ion, and, as one may say, take counsel and stnve together to make us wise and happy .. These are our sight and our hearing, and so admua~ly are theY formed that they are not only more easily, and may be more extem:ivelv educated than any of our ~th_er senses, but we can fwighten their powers by artlficml means. fh" The speaking-trumpet augments the sound o 1m who speaks, and the hearing-tr~mpet concentrates and strencrthens the sound to btm who bears; and those wh; are acquainted with the observe~ laws of sound can so manage matters as that a whts_pe~· can pass silently over a crowd, and be .h~an;I d1st:tnctly by a more distant person by whom 1t IS mtended to be heard. Sound also may be doubled and redoubled by reflection from surfaces ; and it is very possible to hear one of those reflected sounds when the original sound is not heard. There i~ a very famil~ar illustration of that. If you are m a house with equal windows, equally open on all sides of it, and if it thunders, or if ordnance fire, or the bell tolls, or any other loud sound is produced, you are utteFlY unable to tell on which side of the bouse the soundmg body is situated. If there are window_s onl~ on on_e side of the llpartment, you get a notion ot the direction of the sound; but it is probable that notion is a wrong one, because the room has four sides ; and unless you have something else to guide yol:lr condusion, you invariably suppose that the sound IS upon the side where the open windows are. The ear is a beautiful instrument, and the degree of nicety to which it can be educated i~ quite llstonishing; but still we are unable so to understa~d the instruments or analyze the process of hearmg as ' to be able to say in what it consists; and, as a direct means of observing nature, pleasure. rather than information is what it brings us. We !).now that sound .is produced by some sort ~f motion in th~ solL'lililJS UNCERTAINTY OF SOUNDS. 79 body, and that it is propagated throucrh the air so that what we immediately hear is realh~ the air ~nd n~t the body the motion of which first oricrit~ates the sound. It _also goes _in ~h~ direction oppo0site to that of ~he motwn by whtch It IS originally produced; and ag<l:mst the rnotwn of the air which is the medium of It, _th~~gh t~at motion both retards it~ progress and duntmshes 1ts loudness, yet not to the same extent as the motion of the air. The wind renders ~ound l~ss a_udible; but _the audibility is diminished I~ the. dtrectwn of the wmd as well as in the opposite dtrectwn, though not quite to the same extent. When a coach is on th~ _road, and not in sight, we ~an hardly tell w~ether It ts before us or behind; and If there b~ any thmg near us that will echo the sound, the so_undmg body may appear to be sometimes on one stde of us, and sometimes on another. The swelling and sinking of t_h~ sound are the only means that we have of ascertammcr whether it is comin(J' nearer ~o us or going farth~r away; and there ar~ many circumstances by which we may be deceived even then. A clump of trees, or any other object tha_t ca_n deaden the sound, will make us think that whtc~ IS actually approaching us is retiring; and the ~learm_.g ~f such an obstacle will mr~ke that which m reality ts approaching be heard as if it were goincr away. 'J'hus the e~r has, in itself, no more powe~ of enablmg us to d1scover that the voice which we hear in nature is the true voice, than it has of letting us know that what our fellow-men tell us i~ the truth It is principally on account of this want of con~ nexion between the hearing of sounds, and knowledge of the nature, or even the existence of the sounding body, that we are more startled by sudden, loud, and unusu~l sounds than by any other sudden and .strong a~e~twn of the senses. In the discharging of fire~rms, It ts the report which frightens both men and amm~ls, and not the bullet, though the report is pe.rfect..l:)' lWlO.Cen4 a.u.d fue bullet. cardes wounds and |
