Page images
PDF
EPUB

NATURAL HISTORY.

CENTURY III.

Experiments in consort touching the motions of sounds, in what lines they are circular, oblique, straight, upwards, downwards, forwards, backwards.

201. ALL sounds whatsoever move round; that is to say, on all sides; upwards, downwards, forwards, and backwards. This appeareth in all instances.

202. SOUNDS do not require to be conveyed to the sense in a right line, as visibles do, but may be arched; though it be true, they move strongest in a right line; which nevertheless is not caused by the rightness of the line, but by the shortness of the distance; linea recta brevissima. And therefore we see if a wall be between, and you speak on the one side, you hear it on the other; which is not because the sound passeth through the wall, but archeth over the wall.

203. IF the sound be stopped and repercussed, it cometh about on the other side in an oblique line. So, if in a coach one side of the boot be down, and the other up, and a beggar beg on the close side; you will think that he were on the open side. So likewise, if a bell or clock be, for example, on the north side of a chamber, and the window of that chamber be upon the south; he that is in the chamber will think the sound came from the south.

204. SOUNDS, though they spread round, so that there is an orb or spherical area of the sound, yet they move strongest, and go farthest in the fore-lines, from the first local impulsion of the air. And therefore in preaching, you shall hear the preacher's voice better before the pulpit, than behind it, or on the

[merged small][ocr errors]

So a harquebus, or

sides, though it stand open.
ordnance, will be farther heard forwards from the
mouth of the piece, than backwards, or on the sides.

205. IT may be doubted, that sounds do move better downwards than upwards. Pulpits are placed high above the people. And when the ancient generals spake to their armies, they had ever a mount of turf cast up, whereupon they stood; but this may be imputed to the stops and obstacles which the voice meeteth with, when one speaketh upon the level. But there seemeth to be more in it; for it may be that spiritual species, both of things visible and sounds, do move better downwards than upwards. It is a strange thing, that to men standing below on the ground, those that be on the top of Paul's seem much less than they are, and cannot be known; but to men above, those below seem nothing so much lessened, and may be known: yet it is true, that all things to them above seem also somewhat contracted, and better collected into figure: as knots in gardens shew best from an upper window or terras.

206. BUT to make an exact trial of it, let a man stand in a chamber not much above the ground, and speak out at the window, through a trunk, to one standing on the ground, as softly as he can, the other laying his ear close to the trunk: then via versa, let the other speak below, keeping the same proportion of softness; and let him in the chamber lay his ear to the trunk and this may be the aptest means to make a judgment, whether sounds descend or ascend better.

Experiments in consort touching the lasting and perishing of sounds; and touching the time they require to their generation or delation.

207. AFTER that sound is created, which is in a moment, we find it continueth some small time, melting by little and little. In this there is a wonderful error amongst men, who take this to be a continuance of the first sound; whereas, in truth, it is a renovation, and not a continuance; for the body percussed hath, by reason of the percussion, a trepi

a

dation wrought in the minute parts, and so reneweth the percussion of the air. This appeareth manifestly, because that the melting sound of a bell, or of string strucken, which is thought to be a continuance, ceaseth as soon as the bell or string are touched. As in a virginal, as soon as ever the jack falleth, and toucheth the string, the sound ceaseth; and in a bell, after you have chimed upon it, if you touch the bell the sound ceaseth. And in this And in this you must distinguish that there are two trepidations: the one manifest and local; as of the bell when it is pensile: the other secret, of the minute parts; such as is described in the ninth instance. But it is true, that the local helpeth the secret greatly. We see likewise that in pipes, and other wind-instruments, the sound lasteth no longer than the breath bloweth. It is true, that in organs there is a confused murmur for a while after you have played; but that is but while the bellows are in falling.

208. It is certain, that in the noise of great ordnance, where many are shot off together, the sound will be carried, at the least, twenty miles upon the land, and much farther upon the water. But then it will come to the ear, not in the instant of the shooting off, but it will come an hour or more later. This must needs be a continuance of the first sound; for there is no trepidation which should renew it. And the touching of the ordnance would not extinguish the sound the sooner: so that in great sounds the continuance is more than momentany.

209. To try exactly the time wherein sound is delated, let a man stand in a steeple, and have with him a taper; and let some vail be put before the taper; and let another man stand in the field a mile off. Then let him in the steeple strike the bell; and in the same instant withdraw the vail; and so let him in the field tell by his pulse what destance of time there is between the light seen, and the sound heard for it is certain that the delation of light is in an instant. This may be tried in far greater distances, allowing greater lights and sounds.

[ocr errors]

10. It is generally known and observed that light, and the object of sight, move swifter than sound: for we see the flash of a piece is seen sooner than the noise is heard. And in hewing wood, if one be some distance off, he shall see the arm lifted up for a second stroke, before he hear the noise of the first. And the greater the distance, the greater is the prevention as we see in thunder which is far off, where the lightning precedeth the crack a good space.

211. COLOURS, when they represent themselves to the eye, fade not, nor melt not by degrees, but appear still in the same strength; but sounds melt and vanish by little and little. The cause is, for that colours participate nothing with the motion of the air, but sounds do. And it is a plain argument, that sound participateth of some local motion of the air, as a cause sine qua non, in that it perisheth so suddenly; for in every section or impulsion of the air, the air doth suddenly restore and reunite itself; which the water also doth, but nothing so swiftly.

Experiments in consort touching the passage and interceptions of sounds.

IN the trials of the passage, or not passage of sounds, you must take heed you mistake not the passing by the sides of a body, for the passing through a body; and therefore you must make the intercepting body very close; for sound will pass through a small chink.

212. WHERE sound passeth through a hard or close body, as through water; through a wall; through metal, as in hawks bells stopped, etc. the hard or close body must be but thin and small; for else it deadeth and extinguisheth the sound utterly. And therefore in the experiment of speaking in air under water, the voice must not be very deep within the water for then the sound pierceth not. So if you speak on the farther side of a close wall, if the wall be very thick you shall not be heard; and if there were an hogshead empty, whereof the sides were some two foot thick, and the bunghole stopped; I conceive the resounding sound, by the communica

[ocr errors]

tion of the outward air with the air within, would be little or none: but only you shall hear the noise of the outward knock, as if the vessel were full.

213. IT is certain, that in the passage of sounds through hard bodies the spirit or pneumatical part of the hard body itself doth co-operate; but much better when the sides of that hard body are struck, than when the percussion is only within, without touch of the sides. Take therefore a hawk's bell, the holes stopped up, and hang it by a thread within a bottle glass, and stop the mouth of the glass very close with wax; and then shake the glass, and see whether the bell give any sound at all, or how weak: but note, that you must instead of the thread take a wire; or else let the glass have a great belly; lest when you shake the bell, it dash upon the sides of the glass.

214. IT is plain, that a very long and downright arch for the sound to pass, will extinguish the sound quite; so that that sound, which would be heard over a wall, will not be heard over a church; nor that sound, which will be heard if you stand some distance from the wall, will be heard if you stand close under the wall.

215. SOFT and foraminous bodies, in the first creation of the sound, will dead it; for the striking against cloth or furr will make little sound; as hath been said: but in the passage of the sound, they will admit it better than harder bodies; as we see, that curtains and hangings will not stay the sound much; but glass windows, if they be very close, will check a sound more than the like thickness of cloth. We see also in the rumbling of the belly, how easily the sound passeth through the guts and skin.

216. IT is worthy the inquiry, whether great sounds, as of ordnance or bells, become not more weak and exile when they pass through small crannies. For the subtilties of articulate sounds, it may be, may pass through small crannies not confused; but the magnitude of the sound, perhaps, not so well.

« PreviousContinue »