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A42318 A philosophical essay of musick directed to a friend. Guilford, Francis North, Baron, 1637-1685. 1677 (1677) Wing G2216; ESTC R38780 22,387 38

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A Philosophical ESSAY OF MUSICK Directed to a FRIEND Imprimatur Feb. 3 d 1676 7 Guil. Sill. LONDON Printed for John Martyn Printer to the Royal Society at the Bell in Saint Paul's Church-Yard 1677. SIR HAving often tyred you with Discourses of several Parts of Musick wherein you desired to receive satisfaction without obtaining the Effect I proposed to my self I reflected upon the saying That no man understands that which he cannot so express as to make another understand it and doubted whether the Hypothesis I entertained were not founded upon Errours which I had swallowed without any due examination I resolved for tryal of it to trace my Notions as near their Principles as I could and set them down in method that I might discover whether they were well deduced from one another and from such Experiments as I had in memory Having done this I send them to you as the severest judge I know It has not been your custome to flatter me and now I desire your censure if I may impose it upon you to give it in writing wherein you will be obliged to quote what I say truly before you object to it and to stand to those Allegations and Inferences you will set down for your own in both which respects I had great disadvantage in Discourse I shall prevent you in condemning the stile for being too contracted and obscure and you must take the fault to your self when you know it does not proceed from the aversion I have to Philologie but that I thought it would be labour lost to enlarge when writing to so great a Philosopher and Musician as you are I cannot fail of being understood In other things I expose it to you and if I shall receive plain Confutations it will not much disappoint or mortifie me for I have hardly in my whole Life made one set experiment upon this Subject nor know many of the Instruments I have spoken of But what I heard from others or occasionally observed I laid up in mind and established this Systeme which I shall be glad to lose if I may improve my Knowledge by your Discoveries This may seem strange to you considering how fond men are of their own Inventions At the worst I hope for this fruit of my pains that you will make such Experiments as your Curiosity will suggest whilst you read this and let me know the success of them though I may thereby be driven out of his Hypothesis perhaps I shall receive light towards another which you may believe I shall take as much pleasure in making as you or any body else can to destroy I am SIR Your most Faithfull Friend and Servant Of SOUND MY design being to explain the nature of Musick it will not be improper to enquire first concerning the cause of Sound and here though I cannot hope to give full satisfaction because our Senses want subtilty to discover the motions of the minute parts of the Air whereupon it depends yet perhaps I may assign a possible cause for the producing of Sound the knowledge whereof will give some ease to the wondring Philosopher and if I have the good fortune to shew a probable cause the Curious will acquiesce from any farther enquiry which is all the benefit they can have by speculations of this nature The Phaenomena of Sound which I think considerable are these 1. It may be produced in the Torricellian vacuity 2. It causes motion in solid bodies 3. It is diminished by interposition of solid bodies and 4. If the bodies interposed are very thick its passage is wholly obstructed 5. It seems to come to the Ear in strait lines when the object is so scituated that it cannot come in a straight line to the Ear. 6. When the air is not in motion its extent is sphaerical 7. When there is a wind the sphaere is enlarged on that part to which the wind blows and diminished on the contrary part 8. That it arrives not to the Ear in an instant but considerably slower than sight 9. That it comes as quick against the wind as with it though not so loud nor so far There are many other observable Appearances and more will daily occurre to the Curious upon Experiments but the consideration of these qualities of Sound and the visible actions that produce it hath made me entertain the following Hypothesis I suppose the air we breath in to be a mixture of divers minute bodies which are of different sorts and sizes though all of them are so small as to escape our senses the grosser of them are elastical and are resisted by solid bodies which are in no sort pervious to them the smaller parts pass through solid bodies but not with that ease but that upon a sudden and violent start of them they shock the parts of solid bodies that stand in their way and also the grosser parts of the air and there may be another degree of most subtil Ethereal parts with which the interstices of these and all other bodies are repleat which find freer passage every where and are capable of no compression and consequently be the medium and cause of the immediate communication of sight The middle sort of these I esteem the medium and cause of Sound and that at any time when the grosser air is driven off any space and leaves it to be possest by these and other more subtil bodies and returns by its elasticity to its former place then are these parts extruded with violence as from the center of that space and communicate their motion as far as the sound is heard Or when any solid body is moved with a sudden and violent motion these parts must be affected thereby for as these parts are so much resisted by solid bodies as to shock them so on the contrary they must needs be moved by the sudden starting of solid bodies So that sound may be caused by the tremble of solid bodies without the presence of gross Air and also by the restitution of gross Air when it has been divided with any violence We see a Bell will sound in the Torricellian space and when the Air is divided with any sudden force as by the end of a Whip having all the motion of the Whip contracted in it and by a sudden turn throwing off the Air by accension as in Thunder and Guns or by any impression of force carrying it where other Air cannot so forcibly follow as upon compressing of Air in a bladder till it breaks or in a Potgun a sudden crack will be caused I shall leave others to apply this Hypothesis to the afore mentioned Phaenomena which they may easily do and proceed to the discourse of Musick where I am in its due place to shew how this action that causes sound is performed by the several instruments of Musick Of a TONE A Tone is the repetition of Cracks or Pulses in equal spaces of time so quick that the interstices or intervals are not perceptible to
in mind and are as it were included in any Tone This being considered it will appear that there can be no other variety of coincidence within the compass of seven pulses that is not allowed in Musick and produces some Chord For ⅓ is as ⅔ 2 being the Octave to 1. ⅕ is as ⅘ 4 being in Octave to 1. ⅖ as ⅘ 2 6 as ⅔ ⅙ as 4 6 as ⅔ And the eighth coincident pulse in a sixth flat comes in upon this contemplation but as the reverse of a third sharp ⅝ being the reverse of 5 4 and the other sixth ⅗ is the reverse of 6 5. So that there can be no other coincidences under the distance of the seventh pulse but what have the names of Chords or the Octaves and we are not to wonder why there are no more concording Notes How TONES are produced and of assistances to the SOUND by Instruments WHerever a Body stands upon a Spring that vibrates in equal Termes such a Body put into motion will produce a Tone which will be more grave or acute according to the velocity of the returns Therefore strings vibrating have a Tone according to the bigness or tension of them and Bells that vibrate by cross ovals produce Notes according to the bigness of them or the thickness of their sides and so do all other bodies whose superficies being displaced by force results by a spring which carries it beyond its first station It is easie to comprehend how every pulse upon such vibrations causes Sound for the gross Air is thrown off by the violence of the motion which continues some moment of time after the return of the vibrating Body whereupon some space must be left to that subtil matter which upon the result of the Air starts as from a Centre which action being the same I supposed to be the cause of Sound is repeated upon every vibration It is more difficult to shew how Tones are made by a Pipe where there are no visible vibrations I will consider the frame of a Pipe and the motion of the Air in it and thereby attempt to find the cause of the Tone of a Pipe and the pulse that gives the Sound There is in any Pipe a Cavity of a certain gage or bigness which is exposed to the outward Air but in some parts of it and according to that Cavity is the Tone of the Pipe The Air in any Cavity being capable of being compressed by outward force if the Cavity be large easily yields to a compression but if it be small is more hardly compressed When the compressing force ceases the Body that was compressed with difficulty flies out with sudden violence that which is more easily compressed restores it self not so soon whereby it happens that every Cavity has a certain Tone according to the measure of the vibrations of the Air in it which it will keep what way soever the force comes to it As the water in a Shallow or Greek moved by the large waves of the Sea retains not a motion in such huge waves but in waves proportionable to its own bigness and depth Hereupon I conclude That any Pipe whether made of Wood Stone Glass or Metal has a certain and determinate Tone according to its Gage and Cavity which is the natural Tone which will be produced by blowing it If the Cavity be small the Sound will be acute and may be made more acute by apertures whereby the Cavity is diminished and the inclosed Air exposed to the outward Air in greater measure When I say the Tone is according to the proportion of the Cavity let the Pipe be made of what it well I do not deny but that if the materials of the Pipe be soft and yielding it may give some small alteration to the Tone from what it would be if they were of a substance hard and firm where the impelling Air would find a more brisk resistance but the difference is inconsiderable and the spring of the Air depending mainly upon the greatness of the Cavity I take no notice of it To shew how the pulses are caused whereby the included Air is put into this motion it is necessary to observe the frame of a Pipe which chiefly consists in having a long slit through which the Air is blown in a thin film against or very near a solid edge that is at some distance opposite to it in such manner that the intermediate space is covered by the stream of Air. This film of Air on the one side is exposed to the outward Air and on the inside is defended from it by the sides of the Pipe within which the Air inclosed in the Pipe stagnates whilst the outward Air is by the blast put into a vortical motion The vortical motion or Eddy on the outside is so strong that there not being a balance to that force on the inside the film of Air gives way and the Eddy bears into the Pipe but is immediately overcome by the blast which prevails untill the Eddy overcomes it again and so there is a crossing of streams by turns and pulses which causes the voice of the Pipe the gross Air of one stream being thrown off by the interposition of the other These vicissitudes or termes will answer the Tone of the Pipe according to the gage of its cavity for the spring of the included Air helps toward the restitution of the blast and eddy in their turns which causes those turns to comply with the Tone of the Pipe and therefore the same blast will cause several Tones if the gage or measure of the included Air be changed by apertures in the side of the Pipe But there must be some proportion between the mouth so I call that part of the Pipe where the voice is and the gage of the Pipe for though the pulses will be brought to comply with the Tone of the Pipe in any reasonable degree yet when there is great disparity it will not do so as if the Pipe be too long for the proportion of the diameter the pulses at the mouth cannot be brought to so slow termes as to answer the vibrations of the included Air therefore the Pipe will not speak unless it can break into some higher Note If the filmy stream of Air be too thick the Pipe will not speak because the eddy cannot break through if the opposite edge be too remote the stream cannot entirely cover the aperture for it mixes with the outward Air and is more confused the farther it is from the vent or passage whereby some outward Air may have communication to make an opposite eddy on the inside of the stream For the same reason if there be the least aperture in the region of the mouth of the Pipe it will not speak at all Hence is it that the voice of Organ Pipes is so tender and nice but shrill whistles depend not upon this ground for they are made in any small cavity where the blast is so applyed that