while thofe at Reft appear not in the least to have been fhocked. I do not know that I ever faw an Effect in Nature fo very ftupendous, and, at the fame Time, capa le of being demonftrated in fo fimple a Manner.

Clean. I shall entertain you with more of the Wonders of Nature in this Way at another Time: At prefent, I think I have kept your Mind fufficiently upon the Stretch, and therefore fhall poftpone the Confideration of thofe called Wind-inftruments to the next Opportunity.

DIALOGUE XXII.

The Rationale of different Kinds of MUSICAL INSTRUMENTS, continued.

You

Euphrofine.

have given me a large and particular Account of many Sorts of mufical Inftruments, particularly those whofe delightful Effects are produced by the Vibrations of Strings; and you promised me, at the Conclufion of our laft Conference, that the Subject of our next mufical Speculation was to be the PHILOSOPHY of Wind-inftruments: Of this Sort, I must confefs, I have but a very flender Notion, and here, if you do not take Care, you will foon get out of my Latitude.

Cleon. I fhall trouble you with nothing very myfterious on this Head; for all Kind of Wind-inftruments, from the Jews Harp to the ORGAN, depend upon one fimple Principle, viz. the vibrating Motion of condenfed Air; for as all ftringed Instruments produce their Effects by exciting Vibrations in the Air by the Vibrations of their Strings, fo all Kind of hollow Pipes may have their contained Air impreffed, and condensed by the different Force of the Breath, or Blaft from the Mouth, or by other Means, and thereby the Action of that condensed Air yariously modified, and which, communicated to the external Air, will be the Caufe of as great a Diversity of

Vibrations therein, and confequently of mufical Sounds or Notes, which, as I have. fhewn you, confift in nothing more than the Pulfes of Air properly modified and modulated for that Purpose.

Euphrof. Then I fuppofe, by what you say, Cleonicus, if a Perfon applies a common Trumpet to his Mouth, and puts the Air in Motion by the Force of his Breath, the Vibrations of that condensed Air will make a loud SoundThen a Person blowing through a Trumpet of the fame Dimenfion with fuch a Force of Breath as will condense the Air to twice the Degree, will cause the Vibrations to be twice as quick, and, confequently, to produce in the external Air a Sound, whofe Note or Tone shall be twice as high, or more acute than the other: And therefore the Tones, or Notes of those two Trumpets will be an Octave diftant from each other: Am I not right fo far, Cleonicus?

Cleon. You certainly are, my Euphrofyne: And if the second Person was to agitate the Air with a lefs Force of Breath, fo that its Vibrations thould be in Proportion to those of the other Trumpet, as 3 to 2, then would the Notes of the two Trumpets be that Concord called the Fifth. If the Breath be farther weakened, fo as to cause but 4 Vibrations in this Trumpet to 3 of the First, the latter will be a Fourth above the former, and fo on for a Third, Second, &c. whence it appears, that two Trumpets being founded together, are capable of producing all the Variety of mufical Sounds in common with ftringed Inftruments.

Euphrof. So far I understand you pretty clearly, and, at the fame Time, I fee in general the Reason why a TRUMPET, French HORN, &c. is of itself a mufical Inftrument; becaufe, by variously agitating the Air with different Forces of the Breath, any Variety of mufical Notes may be produced by Succeffion, and, confequently, any Piece of Mufic may be performed in a fingle Part by thofe Inftruments, and two of them together in Concert; and becaufe of the Greatness of their Sound, or Loftinefs of their Notes, this Sort of Wind-mufic is generally appropriated to all joyful and triumphal Occafions, and are particularly pleafing in the Gloom of a ferene Night, and have their Effects

greatly

greatly heightened by their Reverberation from an extended Surface of Water. In this Trumpet-mufic, the Air feems not to be confined or agitated in the fame Manner as in those Pipes or Tubes we call FLUTES: Pray, how am I to understand the Effect of this Sort of Windinftruments?

Cleon. The Air in the Body of any Pipe or Flute, will, by other Air forced in upon it, be put into Motion, and being thereby more or lefs condenfed, will have fuch Vibrations excited as are proportionably quicker or flower; and thefe, by Means of the Holes producing fimilar Vibrations in the external Air, will caufe all that Variety of mufical Sounds, as before: But the Notes of thofe Sounds will be variable, according to the Bulk and Length of the included Column, or Cylinder of Air; for the larger the Tube or Pipe, the greater will be the Quantity of Air to be put in Motion by the fame Force of the Breath, and, confequently, the lefs will be its Condenfation, therefore the flower its Vibrations, the lower will be the Note or Tone of Sound which it emits.But as one Length of String will produce only one Sort of Note, (with the fame Degree of Tenfion) fo one Body or Quantity of Air will be capable only of one Degree of Vibration, and therefore of producing only one Note, which, indeed, may be higher or lower, as the Force of the Breath may be stronger or weaker impreffed. But what I now fay must be understood to relate to the common Method of founding thofe Inftruments; for, if you pleafe, you may blow with Force enough to caufe Vibrations twice as quick in the fame Body of Air, and confequently to make the Sounds emitted an Octave one above another: But you cannot, in this Cafe, produce any Note between the Octaves, which is fomething of a very odd and extraordinary Nature.

Euphrof. Pray, Cleonicus, what is it makes that which is called the Pitch-pipe of fuch general Ufe in tuning musical Instruments?

Cleon. As we are now difcourfing of Wind-mufic of the tubular Kind, your Question is very apropos, and the Rationale of the Pitch-pipe will be very easy to conceive from what hath been faid; For as the Vibrations

of

of the Air will be proportioned to its Quantity in a uniform Tube, whether fquare or round, it matters not; therefore as you increase or diminish the Length of the Bore, or Capacity of the Pipe, by the folid Part that is moveable in it, fo you may give fuch Lengths to the included Body of Air as thall render it productive of Vibrations of any given Degree of Velocity, and thereby produce any given Nate of an Octave.

Euphraf. If I understand you right, when the Air of the Pipe has its full Length, it will produce the loweft or Bafe Note; but when the folid Part is placed fo far in the Pipe as to diminish the Length of the Body of included Air, by one Half, and the Note be founded, it will be now an Octave above the former, or twice as high Is it not fo, Cleonicus?

Cleon. It is, my Euphrofyne, just as you have expreffed it:- -And farthermore, if the Stopple be moved ftill farther up the Pipe, fo as to leave the Column of Air but of its first Length, its Vibrations will be then twice as quick as in the laft Cafe, and therefore will produce a Note twice as high, and confequently will be a double Octave above the Bafe Note:Therefore it is, that this folid Part or Stopple may be confidered as a Monchord in its whole Length, and may be fo divided into a Hundred equal Parts, in the fame Manner as I obferved to you of the Bafe or Key-note when it was a String: But here the Beginning of the Divifion is from the End that enters the Pipe; therefore, if you place it in the Tube to the Divifion 50, it will found an Octave; but if you draw it back to 53, the Note will be a 7th greater;if you stop at 60, it will be a 6th greater;and after that at 40%, the Fifth Note will be produced; again, by placing it to 75, you have the Fourth Note;- -then again at 80, and you have the Third Note; -and, laftly, against 80, you have the Second Note, or that next to the Key or Bafe Note-Thus, any Note of the Octave may be produced by the Pitch-pipe: And if the Notes in this firft Octave be not high enough, you may go an Octave higher on the fame Monochord, and fo have a very great Extent of Notes in this Pipe.

Euphrof. Then, I prefume, the Reafon why it is called a Pitch-pipe is because, by this Means, he that tunes the Harpsichord, or other Inftrument, may be thereby able to pitch the Note, or Tune, to the proper Height above, or Distance from the Bafe Note; fo that any of the feven Notes in the Octave may be ascertained by this Pipe: And thus all the Octaves, and confequently the whole Inftrument, may be put into Tune, at any Time, by this mechanical Method.I fuppofe, the Rationale of all Wind-inftruments is nearly the fame; as you have given me to understand, that Notes or Sound of this Kind depend upon, and result from the different Agitations and Vibrations of the included Air in the Pipes.

Cleon. What you obferve is in general very juft : But there is, at the fame Time, great Art and Contrivance required in the Inftrument-maker, with respect to the internal Structure and Bore of the Tube, or Pipe; and alfo the Form and Size of the Holes, or Ventages, by which thofe Sounds are modulated by the Fingers in Flutes, Hautboys, &c.— -But the Capital, or moft noble and magnificent of all the Inftruments for Wind-mufic is, the ORGAN, fo called by Way of Pre-eminence; because the Word Organ fignifies, in the original Greek, nothing more than an Inftrument.-The Principle of Organ-mufic is in itself very fimple and eafy, as I have already fhewn; nor is its Structure fo very difficult, or complicated, as might be imagined from its pompous Appearance.

Euphrof. The Afpect and Effect of the Organ are both in a fuperlative Degree: I am always ravifhed with its majestic Form, as well as with its divine and celeftial Sounds. I think it is with the greatest Propriety confecrated to the Worship of the Deity; as it must be allowed greatly to affift all that Part of our Devotion which relate to facred Mufic and Harmony, fuch as finging Anthems, Pfalms of Praife, &c. and fomething of this Kind we find has always been in Ufe in Royal Chapels, and other chief Places of Worship.- -But methinks, I fhould be glad to know fomething of the internal Structure of this Inftrument, as I have never yet had an Opportunity of gratifying my Curiofity by an Infpection thereof.