An Introductory Essay to the Doctrine of Sounds, Containing Some Proposals for the Improvement of Acousticks; As It Was Presented to the Dublin Society Nov. 12. 1683. by the Right Reverend Father in God Narcissus Lord Bishop of Ferns and Leighlin

An introductory Essay to the doctrine of Sounds, containing some proposals for the improvement of Acousticks; As it was presented to the Dublin Society Nov. 12. 1683. by the Right Reverend Father in God Narcissus Lord Bishop of Ferns and Leighlin. Being to treat of the Doctrine of Sounds, I hold it convenient to premise something in the general concerning this Theory; which may serve at once to engage your attention, and excuse my pains, when I shall have recommended them, as bestowed on a subject not altogether useless and unfruitful. And for this purpose I shall omit to speak any thing of the Excellency of the matter in hand; though it might be celebrated by Arguments drawn from several Topicks, and particularly from this, that new discoveries and improvements may be made, both as to the Generation, Propagation and Reception of Sounds into the Sense; which in a peculiar manner agrees to this, above the object of any other Sense whatsoever. I shall, I say, omit these things, and apply myself wholly to the usefulness of the Theory, that we are now falling upon; which I think cannot better be discovered, than by making a comparison 'twixt the Senses of Seeing and Hearing as to their improvements. I mean, by shewing, that this later of Hearing, is capable of all those improvements which the Sense of Seeing has received from Art; besides many more advantages, that the Ear may enjoy, by the help of our Doctrine, above the Eye; all which moreover will be of as great benefit to mankind, as any thing that Opticks have yet discovered, if not of greater; which, with some other preeminencies that it has upon another Score, will happily render Acousticks the nobler Science of the two. In order to the making good what I but now promised of the Comparison of these two Faculties of Seeing and Hear- Hearing, as to their improvements, I observe, That Vision is threefold, Direct, Refracted, and Reflex'd; answerable whereunto we have Optick, Dioptricks, and Catoptricks. In like manner Hearing may be divided into Direct, Refracted, and Reflex'd; whereto answer three parts of our Doctrine of Acousticks; which are yet nameless, unless we call them Acousticks, Diacousticks, and Catacousticks, or (in another sense, but to as good purpose) Phonicks, Diaphonicks, and Cataphonicks. 1. Direct Vision has been improv'd two ways; ex parte Objecti, and ex parte Organivel Medij. 1. Ex parte Objecti Direct Vision has receiv'd advantages by the Arts of Producing, Conserving and Imitating Light and Colours, which are the Objects of Vision. 1. For the Art of Producing Light, we have the Frication of all hard Bodies, that beget Fire; especially of the Flint and Steel; and instead of the Flint, most hard Stones (as well as the Cane) may be us'd to the same effect; as upon trial I have found. Add hereto the lately invented Phosphorus, which is a new and admirable way of producing a Lucid substance by Art, out of a body in itself not Lucid; and therefore may not unfitly be term'd an Artificial production of Light. And then of the Art of Conserving Light, the Lapis Bononiensis is a notable instance; and so happily were the Sepulchral Lamps of the Ancients. 2. As to Colours 'tis the greatest part of the Art of Eyeing to be able to make and fix (that is preserve) them; and the Painters and Limners will own it to be no small part of their Skill to be able well to Mix (that is in effect, to Generate) Colours. 3. For Imitation of Light and Colours 'tis well known how far Perspective with the Art of Limning and Shadowing, have gone therein, which all tend someway to the Advance or Improvement of Direct Vision. Add to all these, That a due Application of Light to the Object renders it Visible, if it were not so before; as appears from a dark room illuminated: or else makes it better and more truly discernable by the Sense of Seeing; if before it might have been discern'd. Hence the same Colour in a divers Light will appear different, and no Picture can well be discern'd or judg'd of, but by it's true Light. Besides, the Limner will assure you, that he can hardly make true work or hit the Air of a face exactly, unless he draw by a North-Light, by reason of the Steadiest of that, and the uncertainty of all other Lights whatsoever. Which things shew, that the Art of duly applying Light to the Object does very much help and improve Vision. So also does the due placing of the Object, as to Height and Distance. But to enumerate all things, that help Direct Vision, would be infinite. 2. Ex parte Organi v.l M.dij Direct Vision has been improved by making use of a Tube, without Glasses, or a man's clos'd hand, to look throw; which admitting into the Eye only the principal rays, that come directly from the Object, do very much strengthen and clear the Sight, by excluding all the Collateral rays, that crowding into the Eye, together with the direct ones, would confound and disturb it, partly by mixing and interfering with the Direct rays, and partly (or rather chiefly) by too much enlightening the fund of the Eye, wherein Vision is truly (though then imperfectly) made. On this is founded the Art of making Spectacles without Glasses; (as well as Tubes) which is done by putting into the Glass-holes (instead of Glasses) two short Tubes of between 3 and 4 inches long (for their length is to be vary'd according to the age or eye of the beholder, and so also is the Diameter of the extremities) which Tubes being made of Spanish Leather (or past-board, or some such like matter) and black'd on the inside, are so to be plac'd, as that the visual rays, receiv'd throw them may meet in one one point (or rather issue out from one point) of the Object standing at such a due distance, as the person may clearly and distinctly see it, or according to his length of Sight (as ABC, in the first Fig.) And these Spectacles may be supposed better for preserving the Sight, than the ordinary ones with Glasses because they represent the Object more naturally, and withal more clearly and distinctly to the Eye, than the other, whose refracted rays being collected together with the right ones in the Glasses, do somewhat confound good Vision; as before. Especially if the visive power be strong enough to be sufficiently determin'd by the right rays alone. For I speak now of preserving a good Eye by these Spectacles; which holds in proportion true also of a bad one. Because those Rays (both right and refracted) being collected and brought so near the Eye (whether good or bad) as the Spectacles are usually plac'd, do too much affect it, both by their own brightness, and also by the brightness of the colours of the Object (when they are bright) which is brought very near also; whereby the Eye is dazzl'd and confounded; unless there be a strong attention and conatus of the Spirits, whereto the bright Rays do certainly engage them; which of necessity weakens Vision; especially if these Glass-spectacles be much us'd. Wherefore the now describ'd new Tube-spectacles, contributing so much to the help and preservation of Sight, may well be counted an improvement of Direct Vision; because they convey the rays to the Eye without any kind of refraction whatsoever. Seeing the same Object also through various holes, plac'd at certain distances, does somewhat alter Vision; but of this perhaps more hereafter. Now as Direct Vision has thus been improv'd; so likewise Direct Hearing partly has already receiv'd, and partly may (by the Doctrine whereof we are treating, if well cul- cultivated) farther receive as great and notable Improvements, both *ex parte* Objecti, and *ex parte* Organi vel Medij. 1. As to the *Object* of hearing, which is Sound, improvement has been and may be made, both as to the *Begetting*, and as to the *Conveying* or *Propagating* (which is a kind of *Conserving*) of Sounds. 1. As to the *Begetting* of Sounds. The Art of Imitating any Sound, whether by *Speaking* (that is pronouncing) any kind of Language, (which really is an Art; and the *Art of speaking* perhaps one of the greatest) or by *whistling* or by *Singing* (which are allow'd Arts) or by *Hollowing* or *Luring*, (which the Huntsman and Faulkner would have to be an Art also) or by *Imitating* with the Mouth (or otherwise) the voice of any Animal; as of *Quails*, *Cats* and the like, or by *Representing* any Sound begotten by the Collision of Solid Bodies or after any other manner; these are all *Improvements* of *Direct Hearing*, and may be improv'd. Moreover the skill to make all sorts of *Musical Instruments*, both Ancient and Modern, whether *Wind Instruments* or *Stringed*, or of any other sort, whereof there are very many (as *Drums*, *Bells*, the *Systrum* of the Egyptians, and the like) that beget (and not only propagate) Sounds; the skill of making these, I say, is an Art, that has as much improved *Direct Hearing*, as an Harmonious Sound exceeds a single and rude one, that is, an *im-musical Tone*, which Art is yet capable of farther Improvement. And I do hope, that by the rules, which may happily be laid down, concerning the *Nature*, *Propagation* and *Proportion* or *Adapting* of Sounds, a way may be found out, both to improve *Musical Instruments* already in use, and to invent new ones, that shall be more sweet and lushious, then any yet known. Besides that by the same means *Instruments* may be made, that shall imitate any sound in Nature, that is not *Articulate*; be it of Bird, Beast, or what thing else soever. 2. The Conveying and Propagating (which is a kind of Conserving) of Sounds, is much help'd by duly placing the Sonorous Body, and also by the Medium. For if the Medium be Thin and Quiescent, and the Sounding body plac'd conveniently, the Sound will be easily and regularly propagated, and mightily conserv'd. I say, 1. If the Medium be Thin and Quiescent; because it otherwise causeth a Refracted Sound; of which afterwards. Hence in a Still Evening or the dead of the night (when the wind ceases) a Sound is better sent out and to a greater distance, then otherwise; though much of this may be ascrib'd to its Refraction also. 2. I say, that the Sonorous Body must be plac'd conveniently, near a Smooth wall, near Water, or a Plain, whose surface is even. 1. Near a Smooth wall, either Plane or Arch'd (Cyclo-dically or Elliptically, rather than otherwise; though a Circular or any Arch will do; but not so well.) Hence in a Church, the nearer the Preacher stands to the wall (and certainly 'tis much the best way to place Pulpits near the wall) the better is he heard, especially by those, who stand near the wall also, though at a greater distance from the Pulpit; those at the remotest end of the Church, by laying their Ears somewhat close to the wall, may hear him easier than those in the middle. Hence also do arise Whispering places. For the voice being applied to one end of an Arch, easily rolls to the other. And indeed were the motion and propagation of sounds but rightly understood, 'twould be no hard matter to contrive Whispering places of infinite variety and use. And perhaps there could be no better or more pleasant hearing a Consort of Musick, than at such a place as this, where the Sounds rouling long together, before they come to the Ear, must needs confoliate and imbody into one; which becomes a true composition of Sounds, and is the very life and soul of Consort. 2. If the Sonorous body be plac'd near Water the sound will easily be convey'd, yet mollified; as experience teacheth us from a Ring of Bells near a river and a great Gun shot off at Sea; which differ much in the strength, and yet softness and continuance or propagation of their Sounds, from the same at land; where the Sound is more harsh and more perishing, or much sooner decays. 3. In a plane a Voice may be heard at a far greater distance, then in uneven ground. The Reason of all which last nam'd Phenomena is the same, because the Sonorous air meeting with little or no resistance upon a Plane (much less upon an Arch'd) smooth superficies, easily rouls along it, without being let or hindred in its Motion, and consequently without having its parts disfigur'd, and put into another kind of Revolution, then what they had at the first begetting of the Sound. Which is the true cause of its Preservation or Progression; and fails much when the air passes over an uneven surface, according to the degrees of its inequality, and somewhat also, when it passes over the plane superficies of a body, that is hard and resisting. Wherefore the smooth top of the Water (by reason of its yielding to the Arch'd air, and gently rising again with a kind of resurge, like to Elasticity, though it be not so; by which resurge it quickens and hastens the motion of the air rouling over it, and by it's yielding preserves it in it's Arch'd Cycloidal or Elliptical Figure) the smooth top of the water, I say, for these reasons, and by these means, conveys a Sound more entire and to a greater distance, than the plane surface of a piece of ground, a wall, or any other Solid Body whatever can do. As for the Speaking Trumpet, by which a voice may be conveyed to a considerable distance, I refer it's consideration to that of Refracted Sounds or Refracted Audition. Thus much of the Improvements of Hearing, that respect it's Obj & which is Sound. 2. The Organ and Medium are to be consider'd. Aud, 1. The Organ, which is the Ear, is helpt much by placing it near a Wall (especially at one end of an Arch, the Sound being begotten at the other) or near the Surface of Water, or of the Earth; along which the Sounds are most easily and naturally convey'd; as was before declar'd. And 'tis incredible, how far a sound made upon the Earth (by the trampling of a Troop of Horses, for Example) may be heard in a still night, if a man lays his Ear close to the ground in a large plane. Otacousticks here come in for helping the Ear; which may be so contriv'd (by a right understanding the Progression of Sounds, which is the principal thing to be known for the due regulating all such kinds of Instruments) as that the Sound might enter the Ear without any Refraction; but as now they are generally made I refer them to Refracted Audition. 2. As to the Medium, I know not how that, by any contrivance of Art, can advantage Direct Hearing, otherwise than I have declar'd already in the propagation or conveyance of Sounds; though to the Refracting or Reflecting of them it may very much conduce; of which presently. And so I have done with the first part of my present undertaking, which is the Comparison of Direct Vision and Audition, as to their Improvements from Art. The rest follow. Wherefore, II. Concerning Refracted Vision and its Comparison, I observe, that Refracted Vision is always made Ex parte Medij; as Reflected is ex parte Objecti. And therefore though Direct Vision may be help'd ex parte Objecti, Medii vel Organis; yet Refracted can be improv'd only ex parte Medij, and Reflected ex parte Corporis oppositi alone. Unless it be in a mixt or compound Vision, that is Refracto-Reflect, when the reflex rayes pass to the Eye through a refracting Medium, such as the Medium Internum, contain'd in the body of the Eye, always is. So that in truth all Vision is Refracted, by an Internal Refraction made in ipso Oculo. And all that I have spoken of Vision holds true of Hearing also, both Refracted and Reflext, and therefore need not be repeated. Refracted Vision arises from the different Density, Figure and Magnitude of the Medium; which is somewhat alter'd also by the divers Incidence of the Visible raies. And so it is in Refracted Hearing, all these Causes concur to its production, and some others to be hereafter consider'd. Now as any Object (a man for example) seen through a thicken'd air, by Refraction appears greater than really he is: So likewise a Sound, heard through the same thickened part of the Atmosphere, will be considerably vary'd from what it would seem to be, if heard through a thinner Medium. And this I call a Refracted Sound. But what this Refraction of Sound is, and how caus'd, may hereafter be discus'd, when the nature and motion or progression of Sounds are well stated. For the Improvement of Refracted Vision artificial Instruments have been made, by grinding or blowing Glasses into a certain Figure, and placing them at due distances; whereby the Object may be (as 'twere) enabled to send forth its raies more vigorously, and the Visible Faculty impowered the better to receive them. And thus also instruments may be contriv'd for the assisting both the Sonorous Body, to send forth its Sound more strongly, and the Acoustick Faculty to receive and discern it more easily and clearly. For, 1. As a fine Glass Bubble, fill'd with clear water, and plac'd before a burning Candle or Lamp, does help it to dart forth its raies to a prodigious length and brightness. So an Instrument may be invented, that apply'd to the Mouth (or any Sonorous body) shall fend forth the voice distinctly to as prodigious a distance and loudness. For if the Stentoro-phonecon (which is but a rude and unartificial Instrument.) does such great feats; what might be done with one compos'd according to the rules of Art? whose make should comply with the Laws of Sonorous Motion (which that does not) and therefore not so much Refract, as to alter and confound the Tone of the Voice and words (as that somewhat does.) Now of what use such an Instrument might be for speaking clearly and articulately at a distance, (and that without altering the Tone of the Voice) whether it be at Sea or at Land (but especially at Sea in tempestuous weather and in the night) is obvious to any man to conceive. 2. As Instruments have been invented to help the Eye. So likewise are there some, and more such there may be, for the Ear. For, 1. As Spectacles and other Glasses are made to help the Purblind and weak Eyes, to see at any competent distance: So there are Otacouflicks (and better may be made) to help weak Ears to hear at a reasonable distance also. Which would be as great a help to the infirmity of Old Age, as the other invention of Spectacles is, and perhaps greater; forasmuch as the Hearing what's spoken is of more daily use and concern to such men, then to be able to Read Books or to View Pictures. 2. As Perspective-Glasses and Telescopes help the Eye to see Objects at a very great distance, which otherwise would not be discernable; in like manner may a sort of Otacouflicks be so contriv'd, as that they shall receive in Sounds made at a very great distance also; but with so much advantage, that the Ear shall be able to hear them, which otherwise would have been inaudible. And these Otacousticks in some respects would be of greater use than Perspectives. For whereas at land Perspectives are many times render'd almost useless, by the interposition of Woods and Mountains, which hinder the Sight from reaching very far: our Otacousticks would, notwithstanding these Obstacles, take in a Sound made some leagues off. Which might be of notable use in the time of War, for discovering the Enemy at a good distance, when he marches or lies incamp'd behind a Mountain or Wood, or any such place of shelter. Yea even at Sea also, where Perspectives are of most use, by reason of the plains of the surface of the Water; Yet sometimes there Otacousticks may be of more benefit, when in dark, hazy weather the air is too thick, or in Stormy Tempestuous weather the Waves rise too high, for the Perspective to be made use of. But whether at Sea or Land, Perspectives become altogether insignificant in the night time (unless it be for viewing the Stars) which is the chief time for using Otacousticks; as it is generally, for Souldiers to take their march, when they would surprise their Enemies. And therefore this sort of Otacousticks have then their chief use, when Perspectives are of no use at all; besides that they may be employ'd in the day time, as well as Perspectives; whence they may (not unfitly) be term'd the most useful Instrument of the two. 3. As Microscopes or Magnifying Glasses, help the Eye to see near Objects, that by reason of their smallness were Invisible before: which Objects they Magnify to a strange greatness: So Microphones or Micracousticks, that is, Magnifying Ear Instruments may be contriv'd after that manner, that they shall render the most minute Sound in nature distinctly Audible, by Magnifying it to an unceivable loudness. By the help hereof we may hear the different cries and tones, as well as by Microscopes see the divers shapes and Figures, of the smallest Animals. 4. As by Polyscopes or Multiplying Glasses, one thing is represented to the Eye as many, whether in the same or different shapes (for so multiplying Glasses may be contriv'd:) so by a Polyphone or Polyacoustick well order'd one Sound may be heard as many, either of the same or a different Note. Insomuch that who uses this Instrument, he shall at the Sound of a single Viol seem to hear a whole Consort, and all true Harmony. By which means this Instrument has much the advantage of the Polyoscope. And thus much may suffice for comparing the Improvements made upon Refracted Seeing and Hearing; I call it Refracted Hearing, because made through a Medium, viz. thick Air or an Instrument, through which the Sound passing is broken or refracted. III. Reflected Vision has been improv'd by the invention of Looking-Glasses and Polished Metals whether Plane, Concave or Convex, and these two last either Spherical, Oval, Cylindrical, Conical, Hyperbolical, or of several other shapes; all which cause a different reflection, and vary the Phenomena. Thus also Reflex'd Audition, made by Echoes, may be improv'd, by contriving several sorts of Artificial Echoes; as 'tis no hard matter to do in almost any place. For (Speaking in the general) Any Sound, falling directly or obliquely upon any dense body, of a Smooth (whether Plane or Arch'd) Superficies, is beat back again and reflected, or does Echo more or less. I say (1) falling directly or obliquely; because, if the Sound be sent out and propagated parallel to the Surface of the Dense Body, or be made so far off and so weak, that it cannot reach it; there will be no reflection of Sound, no Echo. I say (2) upon a body of a smooth superficies; because if the surface of the Corpus Oblatans be uneven, the Air by re- reverberation will be put out of its regular Motion, and the Sound thereby broken and extinguished: So that tho' in this case also the air be beaten back again, yet Sound is not reflected, nor is there any Echo. I say (3) it does Echo more or less, to shew, that when all things are, as is before describ'd, there is still an Echoing, though it be not always heard, either because the Direct Sound is too weak to be beaten quite back again to him that made it; or that it does return home to him, but so weak that without the help of a good Otacoustick it cannot be discern'd; or that he stands in a wrong place to receive the reflected Sound, which passes over his head, under his feet, or to one side of him; which therefore may be heard by a man standing in that place, where the reflected Sound will come, provided no interpos'd body does intercept it; but not by him, that first made it. I shall further make out the comparison 'twixt Reflex'd Vision and Audition by these following Propositions. 1. As a Plane Speculum reflects the Object in its due Dimensions and Colours; allowing for their difference of appearance according to their distance: So a Plane Corpus Obstans reflects the Sound back in its due Tone and Loudness; if allowance be likewise made for the proportionable decreas of the Sound according to its distance. 2. As a Convex Speculum reflects the Object Less, but somewhat brighter or clearer: So a Convex Corpus Obstans repels the Sound (insensibly) smaller; but somewhat quicker (though weaker) than otherwise it would be. 3. As a Concave Speculum reflects the Object Bigger, more Obscure and Inverted: So a Concave Corpus Obstans Echoes back the Sound (insensibly) Bigger, Slower (though stronger) and also inverted; but never according to the order of words. Nor do I think it possible for the Art of man to contrive a Single Echo, that shall invert the Sound and repeat backwards; because then the words last spoken, spoken, that is, which do last occurre to the Corpus Ob- jectans, must first be repell'd; which cannot be. For where in the mean time should the first words hang and be conceal'd or lie dormant? Or how, after such a pause, be reviv'd and animated again into Motion? Yet in com- plicated or Compound Ecchoes, where many receive from one another, I know not whether something that way may not be done. From the determinate Concavity or Archedness of these reflecting bodies it comes to pass, that some of them, from a certain distance or posture, will Eccho back but one determinate Note, and from no other place will they reverberate any; because of the undue position of the Sounding Body. Such an one (as I remember) is the Vault in Merton Colledge in Oxford. 4. As a Speculum takes in and reflects more of its Ob- ject, when placed at a great distance from it, then when nearer; because it reflects according to the apparent magnitude of the body at such a distance, which is less: So also the Echoing body, being removed farther off, reflects more of the Sound, then when nearer. And this is the reason, why some Ecchoes repeat but one Syllable, some one Word, and some many. 5. As Specula's may be so plac'd, that reflecting one upon or into the other, either directly or obliquely, one Object shall appear many; as in Sir Samuel Morlands Glass-room: After the same manner Echoing bodies may be so contriv'd and plac'd, as that reflecting the Sound from one to the other, either directly and mutually, or Obliquely and by Succession, out of one Sound shall many Ecchoes be begotten; which in the first case will be all together & somewhat involved or swallowed up of each other; and thereby confused (as a face in Looking-glasses obverted;) in the other they will be distinct, separate and successing one another; as most multiple Ecchoes do. Moreover a Multiple Echo may be made, by so placing ing the Echoing bodies, at unequal distances, that they reflect all one way, and not one on the other; by which means a manifold successive Sound will be heard (not without astonishment;) one clap of the hands like many, one ha like a laughter, one single word like many of the same tone and accent, and so one Viol like many of the same kind imitating each other. Furthermore, as Specula's may be so order'd, that by Reflection they shall make one single thing appear many different things; as one single man to seem many men differing as to shape and complexion (or a company of men) which I think Sir Samuel Morlands contrivance does not: So may Echoing Bodies also be order'd, that from any one Sound given, they shall produce many Echoes, different both as to their Tone and Intension. (The ground whereof has elsewhere been laid down in a Treatise concerning the Sympathy of Lute-Strings.) By this means a Musical Room may be so contriv'd, that not only one Instrument, played on in it shall seem many of the same sort and size; but even a Consort of (somewhat) different ones; only by placing certain Echoing Bodies so, as that any Note (play'd) shall be returned by them in $3^{rd}$s, $5^{th}$s and $8^{th}$s, which is possible to be done otherwise than was mention'd before in Refracted Audition. I have now done with my Comparison of the two Noblest Senses and Sciences as to their Improvements, wherein I have been thus large, that I might give you a little prospect into the Excellency and Usefulness of Acousticks, and that thereby I might excite all that hear me, to bend their thoughts towards the making of Experiments for the compleating this (yet very imperfect, though noble) Science; a Specimen whereof I will give you in three Problemes, and then present you with the Semiplane of an Acoustick or Phonical Sphear, as an attempt to explicate the great Principle in this Science, which is The Progression of Sounds. The Problems are these, 1. Sonum intendere quousque velis; or, Datum sonum ad datum gradum intendere. 2. Sonum Extendere quousque velis; or, Datum Sonum ad dam distantiam extendere seu propagare. 3. Sonum tranfire ab extreemo ad extremum et non per Medium. 1. The first is, To make the least Sound (by the help of Instruments) as loud as the greatest; a whisper to become as loud as the shot of a Canon. By the help of this Problem the most minute Sounds in nature may be clearly and distinctly heard. 2. The second is, To propagate any (the least) Sound to the greatest distance. By the help hereof any Sound may be convey'd to any, and therefore heard at any distance, (I must add, within a certain, though very large Sphear.) Moreover by this means a Weather-cock may be so contriv'd, as that with an ordinary blast of Wind it shall crie (or whistle) loud enough to be heard many Leagues. Which happily may be found of some use, not only for Pilots in mighty tempestuous weather, when light houses are render'd almost useless: But also for the measuring the strength of Winds, if allowance be made for their different Moisture. For I conceive, that the more drie any wind is, the louder it will whistle cæteris paribus; I say, ceteris paribus, because, besides the strength and drierness of Winds or breath, there are a great many other things (hereafter to be consider'd) that concur to the increase or magnifying of Sounds, begotten by them in an Instrument exposed to their violence, or thrown into. 3. The third Probleme is, That a Sound may be convey'd from one extreme to the other (or from one distant place to another) so as not to be heard in the middle. By the help of this Probleme a man may talk to his freind at a very considerable distance, so that those in the middle space shall hear nothing of what passed betwixt them. Fig. 2. Semiplanum Sphaeræ Phonicae seu Acousticae. You are to conceive that (rude) Semiplane, as Parallel to the Horizon. For if it be Perpendicular thereunto, I suppose the upper extremity will be no longer Circular, but Hyperbolical, and the lower part of it suited to a greater Circle of the Earth. So that the whole Phonical Sphear (if I may so call it) will be a Solid Hyperbola, standing upon a Concave Spherical Base. I speak this concerning Sounds made (as usually they are) nigh the Earth, and whose Sonorous medium has a free passage every way. For if they are generated high in the Air, or directed one way, the case will be different; which is partly design'd in the inequality of that draught.