upon the ground, water, houses, or the like. Water in a river, though a swift stream, is not heard in the channel, but runneth in silence, if it be of any depth; but the very stream upon shallows, of gravel, or pebble, will be heard. And waters, when they beat upon the shore, or are straitened, as in the falls of bridges, or are dashed against themselves, by winds, give a roaring noise. Any piece of timber, or hard body, being thrust forwards by another body contiguous, without knocking, giveth no noise. And so bodies in weighing one upon another, though the upper body press the lower body down, make no noise. So the motion in the minute parts of any solid body, which is the principal cause of violent motion, though unobserved, passeth without sound; for that sound that is heard sometimes, is produced only by the breaking of the air; and not by the impulsion of the parts. So it is manifest, that where the anterior body giveth way, as fast as the posterior cometh on, it maketh no noise, be the motion never so great or swift.

116. Air open, and at large, maketh no noise, except it be sharply percussed; as in the sound of a string, where air is percussed by a hard and stiff body, and with a sharp loose: for if the string be not strained, it maketh no noise. But where the air is pent and straitened, there breath or other blowing, which carry but a gentle percussion, suffice to create sound; as in pipes and wind-instruments. But then you must note, that in recorders, which go with a gentle breath, the concave of the pipe, were it not for the fipple that straiteneth the air, much more than the simple concave, would yield no sound. For as for other wind-instruments, they require a forcible breath; as trumpets, cornets, hunters horns, etc. which appeareth by the blown cheeks of him that windeth them. Organs also are blown with a strong wind by the bellows. And note again, that some kind of wind-instruments are blown at a small hole in the side, which straiteneth the breath at the first entrance; the rather, in respect of their traverse and stop above the hole, which performeth the fipples part; as it is seen in flutes and fifes, which will not give sound by a blast at the end, as recorders, etc.

do. Likewise in all whistling, you contract the mouth; and to make it more sharp, men sometimes use their finger. But in open air, if you throw a stone or a dart, they give no sound; no more do bullets, except they happen to be a little hollowed in the casting; which hollowness penneth the air: nor yet arrows, except they be ruffled in their feathers, which likewise penneth the air. As for small whistles or shepherds oaten pipes, they give a sound because of their extreme slenderness, whereby the air is more pent than in a wider pipe. Again, the voices of men and living creatures pass through the throat, which penneth the breath. As for the Jews-harp, it is a sharp percussion; and, besides, hath the advantage of penning the air in the mouth.

117. Solid bodies, if they be very softly percussed, give no sound; as when a man treadeth very softly upon boards. So chests or doors in fair weather, when they open easily, give no sound. And cart-wheels squeak not when they are liquored.

118. The flame of tapers or candles, though it be a swift motion and breaketh the air, yet passeth without sound. Air in ovens, though, no doubt, it doth, as it were, boil and dilate itself, and is repercussed; yet it is without noise.

119. Flame percussed by air giveth a noise: as in blowing of the fire by bellows; greater than if the bellows should blow upon the air itself. And so likewise flame percussing the air strongly, as when flame suddenly taketh and openeth, giveth a noise; so great flames, while the one impelleth the other, give a bellowing sound.

120. There is a conceit runneth abroad, that there 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 sulphur, 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 cross-barrel 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 in the open air.

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 Saint 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, conservation, and delation of sounds; and the office of the air therein.

124. The cause given of sound, that it should be an elision 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 straightways, 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 bell 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 as 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.

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 further 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