« AnteriorContinuar »
should be a white powder, which will discharge a piece without noise; which is a dangerous experiment if it should be true : for it may cause secret murders. But it seemeth to me impossible; for, if the air pent be driven forth and strike the air open, it will certainly make a noise. As for the white powder, if any such thing be, that may extinguish or dead the noise, it is like to be a mixture of petre and şulphur, without coal. For petre alone will not take fire. And if any man think, that the sound may be extinguished or deaded by discharging the pent air, before it cometh to the mouth of the piece and to the open air, that is not probable; for it will make more divided sounds: as if you should make a crossbarrel hollow through the barrel of a piece, it may be it would give several sounds, both at the nose and at the sides. But I conceive, that if it were possible to bring to pass, that there should be no air pent at the mouth of the piece, the bullet might fly with small or no noise. For first it is certain, there is no noise in the percussion of the flame upon the bullet. Next the bullet, in piercing through the air, maketh no noise; as hath been said. And then, if there be no pent air that striketh upon open air, there is no cause of noise; and yet the flying of the bullet will not be stayed. For that motion, as hath been oft said, is in the parts of the bullet, and not in the air. So as trial must be made by taking some small concave of metal, no more than you mean to fill with powder, and laying the bullet in the mouth of it, half out into the
121. I HEARD it affirmed by a man that was a great dealer in secrets, but he was but vain, that there was a conspiracy, which himself hindered, to have killed queen Mary, sister to queen Elizabeth, by a burningglass, when she walked in St. James's Park, from the leads of the house. But thus much, no doubt, is true; that if burning-glasses could be brought to a great strength, as they talk generally of burningglasses that are able to burn a navy, the percussion of the air alone, by such a burning-glass, would make no noise ; no more than is found in coruscations and lightnings without thunders.
122. I SUPPOSE, that impression of the air with sounds asketh a time to be conveyed to the sense, as well as the impressing of species visible; or else they will not be heard. And therefore, as the bullet moveth so swift that it is invisible; so the same swiftness of motion maketh it inaudible: for we see, that the apprehension of the eye is quicker than that of the ear.
123. All eruptions of air, though small and slight, give an entity of sound, which we call crackling, puffing, spitting, etc. as in bay-salt, and bay-leaves, cast into the fire; so in chestnuts, when they leap forth of the ashes ; so in green wood laid upon the fire, especially roots ; so in candles, that spit flame if they be wet; so in rasping, sneezing, etc. so in a rose leaf gathered together into the fashion of a purse, and broken upon the forehead, or back of the hand, as children use.
Experiments in consort touching production, conser
vation; and dilation of sounds, and the office of the air therein.
124. The cause given of sound, that it should be an elişion of the air, whereby, if they mean any thing, they mean a cutting or dividing, or else an attenuating of the air, is but a term of ignorance; and the notion is but a catch of the wit upon a few instances; as the manner is in the philosophy received. And it is common with men, that if they have gotten a pretty expression by a word of art, that expression goeth current; though it be empty of matter. This conceit of elision appeareth most manifestly to be false, in that the sound of a bell, string, or the like, continueth melting some time after the percussion ; but ceaseth straitways, if the bell, or string, be touched and stayed: whereas, if it were the elision of the air that made the sound, it could not be that the touch of the bell or string should extinguish so suddenly that motion caused by the elision of the air. This appeareth yet more manifestly by chiming with a hammer upon the outside of a beil: for the sound will be according to the inward concave of the bell, whereas the elision or attenuation of the air cannot be but only between the hammer and the outside of the bell. So again, if it were an elision, a broad hammer, and a bodkin, struck upon metal, would give a diverse tone, as well às a diverse loudness: but they do not so; for though the sound of the one be louder, and of the other softer, yet the tone is the same. Besides, in echoes, whereof some are as loud as the original voice, there is no new elision, but a repercussion only. But that which convinceth it most of all is, that sounds are generated where there is no air at all. But these and the like conceits, when men have cleared their understanding by the light of experience, will scatter and break up like a mist. 1.-125. It is certain that sound is not produced at the first, but with some local motion of the air, or flame, or some other medium; nor yet without some resistance, either in the air or the body percussed. For if there be a mere yielding or cession, it produceth no sound; as hath been said. And therein sounds differ from light and colours, which pass through the air, or other bodies, without any local motion of the air; either at the first, or after. But you must attentively distinguish between the local motion of the air, which is but
vehiculum causa, a carrier of the sounds, and the sounds themselves, conveyed in the air. For as to the former, we see manifestly, that no sound is produced, no not by air itself against other air, as in organs, etc. but with a perceptible blast of the air; and with some resistance of the air strucken. For even all speech, which is one of the gentlest motions of air, is with expulsion of a little breath. And all pipes have a blast, as well as a sound. We see also manifestly, that sounds are carried with wind : and therefore sounds will be heard farther with the wind, than against the wind; and likewise do rise and fall with the intension or remission of the wind. But for the impression of the sound, it is quite another
thing, and is utterly without any local motion of the air, perceptible; and in that resembleth the species visible: for after a man hath lured, or a bell is rung, we cannot discern any perceptible motion at all in the air along as the sound goeth; but only at the first, Neither doth the wind, as far as it carrieth a voice, with the motion thereof, confound any of the delicate and articulate figurations of the air, in variety of words. And if a man speak a good loudness against the flame of a candle, it will not make it tremble much; though most when those letters are pronounced which contract the mouth; as F, S, V, and some others. But gentle breathing, or blowing without speaking, will move the candle far more. And it is the more probable, that sound is without any local motion of the air, because as it differeth from the sight, in that it needeth a local motion of the air at first; so it paralleleth in so many other things with the sight, and radiation of things visible; which, without all question, induce no local motion in the air, as hath been said.,
126. NEVERTHELESS it is true, that upon the noise of thunder, and great ordnance, glass windows will shake; and fishes are thought to be frayed with the motion caused by noise upon the water. But these effects are from the local motion of the air, which is a concomitant of the sound, as hath been said, and not from the sound.
127. Ir hath been anciently reported, and is still received, that extreme applauses' and shouting of people assembled in great multitudes, have so rarified and broken the air, that birds flying over have fallen down, the air being not able to support them. And it is believed by some, that great ringing of bells in populous cities hath chased away thunder; and also dissipated pestilent air : all which may be also from the concussion of the air, and not from the sound.
128. A VERY great sound, near hand, hath stệucken many deaf; and at the instant they have found, as it were, the breaking of a skin or parchment in their ear: ,and myself standing near one that lured loud
and shrill, had suddenly an offence, as if somewhat had broken or been dislocated in my ear; and immediately after a loud ringing, not an ordinary singing or hissing, but far louder and differing, so as I feared some deafness. But after some half quarter of an hour it vanished. This effect may be truly referred unto the sound: for, as is commonly received, an over-potent object doth destroy the sense; and spiritual species, both visible and audible, will work upon the sensories, though they move not any other body.
129. In dilation of sounds, the enclosure of them préserveth them, and causeth them to be heard farther. And we find in rolls of parchment or trúnks, the mouth being laid to the one end of the roll of parchment or trunk, and the ear to the other, the sound is heard much farther than in the open air. The cause is, for that the sound spendeth, and is dissipated in the open air; but in such concaves it is conserved and contracted. So also in a piece of ordnance, if you speak in the touch-hole, and another lay his ear to the mouth of the piece, the sound passeth and is far better heard than in the open air.
130. It is further to be considered, how it proveth and worketh when the sound is not enclosed all the length of its way, but passeth partly through open air; as where you speak some distance from a trunk; or where the ear is some distance from the trunk at the other end; or where both mouth and ear are distant from the trunk. And it is tried, that in a long trunk of some eight or ten foot, the sound is holpen, though both the mouth and the ear be a handful or more from the ends of the trunk; and somewhat more holpen, when the ear of the hearer is near, than when the mouth of the speaker." And it is certain, that the voice is better heard in a chamber from abroad, than abroad from within the chamber.
131. As the enclosure that is round about and entire, preserveth the sound; so doth a semi-concave, though in a less degree. And therefore, if you divide a trunk, or a cane into two, and one speak at the