times; and then the last word alone for some times; still fading and growing weaker. And whereas in echos of one return, it is much to hear four or five words; in this echo of so many returns upon the matter, you hear above twenty words for three.

250. THE like echo upon echo, but only with two reports, hath been observed to be, if you stand between a house and a hill, and lure towards the hill. For the house will give a back echo; one taking it from the other, and the latter the weaker.

251. THERE are certain letters that an echo will hardly express; as S for one, especially being principal in a word. I remember well, that when I went to the echo at Pont-Charenton, there was an old Parisian, that took it to be work of spirits, and of good spirits. For, said he, call Satan, and the echo will not deliver back the devil's name; but will say, va t'en; which is as much in French as apage, or avoid. And thereby I did hap to find, that an echo would not return S, being but a hissing and an interior sound.

252. ECHOS are some more sudden, and chop again as soon as the voice is delivered; as hath been partly said: others are more deliberate, that is, give more space between the voice and the echo; which is caused by the local nearness or distance: some will report a longer train of words, and some a shorter; some more loud, full as loud as the original, and sometimes more loud, and some weaker and fainter.

253. WHERE echos come from several parts at the same distance, they must needs make, as it were, a choir of echos, and so make the report greater, and even a continued echo; which you shall find in some hills that stand encompassed theatre-like.

254. IT doth not yet appear that there is refraction in sounds, as well as in species visible. For I do not think, that if a sound should pass through divers mediums, as air, cloth, wood, it would deliver the sound in a different place from that unto which it is deferred; which is the proper effect of refraction. But majoration, which is also the work of refraction,

appeareth plainly in sounds, as hath been handled at full, but it is not by diversity of mediums.

Experiments in consort touching the consent and dissent between visibles and audibles.

WE have obiter, for demonstration's sake, used in divers instances the examples of the sight and things visible, to illustrate the nature of sounds: but we think good now to prosecute that comparison more fully.

Consent of visibles and audibles.

255. BOTH of them spread themselves in round, and fill a whole floor or orb unto certain limits; and are carried a great way: and do languish and lessen by degrees, according to the distance of the objects from the sensories.

256. BOTH of them have the whole species in every small portion of the air, or medium, so as the species do pass through small crannies without confusion: as we see ordinarily in levels, as to the eye; and in crannies or chinks, as to the sound.

257. BOTH of them are of a sudden and easy generation and dilation; and likewise perish swiftly and suddenly; as if you remove the light, or touch the bodies that give the sound.

258. BOTH of them do receive and carry exquisite and accurate differences; as of colours, figures, motions, distances, in visibles; and of articulate voices, tones, songs, and quaverings, in audibles.

259. BOTH of them, in their virtue and working, do not appear to emit any corporal substance into their mediums, or the orb of their virtue; neither again to raise or stir any evident local motion in their mediums as they pass; but only to carry certain spiritual species; the perfect knowledge of the cause whereof, being hitherto scarcely attained, we shall search and handle in due place.

260. BOTH of them seem not to generate or produce any other effect in nature, but such as appertaineth to their proper objects and senses, and are otherwise barren.

261. BUT both of them, in their own proper action, do work three manifest effects. The first, in that the stronger species drowneth the lesser; as the light of the sun, the light of a glow-worm; the report of an ordnance, the voice: The second, in that an object of surcharge or excess destroyeth the sense; as the light of the sun the eye; a violent sound near the ear the hearing: The third, in that both of them will be reverberate; as in mirrors, and in echos.

262. NEITHER of them doth destroy or hinder the species of the other, although they encounter in the same medium; as light or colour hinder not sound,

nor e contra.

263. BOTH of them affect the sense in living creatures, and yield objects of pleasure and dislike: yet nevertheless the objects of them do also, if it be well observed, affect and work upon dead things; namely, such as have some conformity with the organs of the two senses; as visibles work upon a looking-glass, which is like the pupil of the eye; and audibles upon the places of echo, which resemble in some sort the cavern and structure of the ear.

264. BOTH of them do diversly work, as they have their medium diversly disposed. So a trembling me dium, as smoke, maketh the object seem to tremble, and a rising or falling medium, as winds, maketh the sounds to rise or fall.

265. To both, the medium, which is the most propitious and conducible, is air; for glass or water, etc. are not comparable.

266. IN both of them, where the object is fine and accurate, it conduceth much to have the sense intentive and erect; insomuch as you contract your eye when you would see sharply; and erect your ear when you would hear attentively; which in beasts that have ears moveable is most manifest.

267. THE beams of light, when they are multiplied and conglomerate, generate heat; which is a different action from the action of sight: and the multiplication and conglomeration of sounds doth generate an extreme rarefaction of the air; which is

an action materiate, differing from the action of sound; if it be true, which is anciently reported, that birds with great shouts have fallen down.

Dissents of visibles and audibles.

268. THE species of visibles seem to be emissions of beams from the objects seen, almost like odours, save that they are more incorporeal: but the species of audibles seem to participate more with local motion, like percussions, or impressions made upon the air. So that whereas all bodies do seem to work in two manners, either by the communication of their natures, or by the impressions and signatures of their motions; the diffusion of species visible seemeth to participate more of the former operation, and the species audible of the latter.

269. THE species of audibles seem to be carried more manifestly through the air than the species of visibles: for I conceive that a contrary strong wind will not much hinder the sight of visibles, as it will do the hearing of sounds.

270. THERE is one difference above all others between visibles and audibles, that is the most remarkable, as that whereupon many smaller differences do depend namely, that visibles, except lights, are carried in right lines, and audibles in arcuate lines. Hence it cometh to pass, that visibles do not intermingle and confound one another, as hath been said before; but sounds do. Hence it cometh, that the solidity of bodies doth not much hinder the sight, so that the bodies be clear, and the pores in a right line, as in glass, crystal, diamonds, water, etc. but a thin scarf or handkerchief, though they be bodies nothing so solid, hinder the sight: whereas, contrariwise, these porous bodies do not much hinder the hearing, but solid bodies do almost stop it, or at the least attenuate it. Hence also it cometh, that to the reflexion of visibles small glasses suffice; but to the reverberation of audibles are required greater spaces, as hath likewise been said before.

271. VISIBLES are seen farther off than sounds are

heard; allowing nevertheless the rate of their bigness; for otherwise a great sound will be heard farther off than a small body seen.

272. VISIBLES require, generally, some distance between the object and the eye, to be better seen; whereas in audibles, the nearer the approach of the sound is to the sense, the better. But in this there may be a double error. The one because to seeing there is required light; and any thing that toucheth the pupil of the eye all over excludeth the light. For I have heard of a person very credible, who himself was cured of a cataract in one of his eyes, that while the silver needle did work upon the sight of his eye, to remove the film of the cataract, he never saw any thing more clear or perfect than that white needle: which, no doubt, was, because the needle was lesser than the pupil of the eye, and so took not the light from it. The other error may be, for that the object of sight doth strike upon the pupil of the eye directly without any interception; whereas the cave of the ear doth hold off the sound a little from the organ: and so nevertheless there is some distance required in both.

273. VISIBLES are swiftlier carried to the sense than audibles; as appeareth in thunder and lightning, flame and report of a piece, motion of the air in hewing of wood. All which have been set down heretofore, but are proper for this title.

274. I CONCEIVE also, that the species of audibles do hang longer in the air than those of visibles: for although even those of visibles do hang some time, as we see in rings turned, that shew like spheres; in lute-strings fillipped; a fire-brand carried along, which leaveth a train of light behind it; and in the twilight; and the like: yet I conceive that sounds stay longer, because they are carried up and down with the wind; and because of the distance of the time in ordnance discharged, and heard twenty miles off.

275. IN visibles there are not found objects so odious and ingrate to the sense as in audibles. For foul