lest ought not to be shorter than half an inch. The largest glass is nine inches diameter, and the smallest three inches. Between these three are twenty-three dif ferent sizes, differing from each other a quarter of an inch in diameter. To make a single instrument there should be at least six glasses blown of each size: and out of this number one may propably pick thirty-seven glasses (which are sufficient for three octaves with all the semitones) that will be each either the note one wants. or a little sharper than that note, and all fitting so well into each other as to taper pretty regularly from the largest to the smallest. It is true there are not thirtyseven sizes, but it often happens that two of the same size differ a note or half note in tone, by reason of a difference in thickness, and these may be placed one in the other without sensibly hurting the regularity of the taper form.

The glasses being chosen, and every one marked with a diamond the note you intend it for, they are to be tuned by diminishing the thickness of those that are too sharp. This is done by grinding them round from the neck towards the brim, the breadth of one or two inches, as may be required; often trying the glass by a well-tuned harpsichord, comparing the tone drawn from the glass by your finger, with the note you want, as sounded by that string of the harpsichord. When you come nearer the matter, be careful to wipe the glass clean and dry before each trial, because the tone is something flatter when the glass is wet, than it will be when dry: and, grinding a very little between each trial, you will thereby tune to great exactness. The more care is necessary in this, because if you go below your required tone, there is no sharpening it again but by grinding somewhat off the brim, which will afterwards require polishing, and thus increase the trouble.

The glasses being thus tuned, you are to be provided with a case for them, and a spindle on which they are to be fixed. My case is about three feet long, eleven inches every way wide within at the biggest end, and five inches at the smallest end; for it tapers all the way, to adapt it better to the conical figure of the set of glasses. This case opens in the middle of its height, and the upper part turns up by hinges fixed behind. The spindle, which is of hard iron, lies horizontally from end to end of the box within, exactly in the middle, and is made to turn on brass gudgeons at each end. It is round, an inch diameter at the thickest end, and tapering to a quarter of an inch at the smallest. A square shank comes from its thickest end through the box, on which shank a wheel is fixed by a screw. This wheel serves as a fly to make the motion equable, when the spindle, with the glasses, is turned by the foot like a spinning-wheel. My wheel is of mahogany, eighteen inches diameter, and pretty thick, so as to conceal near its circumference about 25lb of lead. — An ivory

pin is fixed in the face of this wheel, and about four inches from the axis. Over the neck of this pia is put the loop of the string that comes up from the moveable step to give it motion. The case stands on a neat frame with four legs.

To fix the glasses on the spindle, a cork is first to be fitted in each neck pretty tight, and projecting a little without the neck, that the neck of one may not touch the inside of another when put together, for that would make a jarring.

These corks are to be perforated with holes of different diameters, so as to suit that part of the spindle on which they are to be fixed. When a glass is put on, by holding it stiffly between both hands, while another turns the spindle, it may be gradually brought to its place. But care must be taken that the hole be not too small, lest in forcing it up the neck should split: nor too large, lest the glass not being firmly fixed should turn or move on the spindle, so as to touch and jar against its neighbouring glass. The glasses thus are placed one in another, the largest on the biggest end of the spindle which is to the left hand; the neck of this glass is towards the wheel, and the next goes into it in the same position, only about an inch of its brim appearing beyond the brim of the first; thus proceeding, every glass when fixed shews about an inch of its brim (or three quarters of an inch, or half an inch, as they grow smaller) beyond the brim of the glass that contains it; and it is from these exposed parts of each glass that the tone is drawn, by laying a finger upon one of them as the spindle and glasses turn round.

My largest glass is G, a little below the reach of a common voice, and my highest G, including three complete octaves. To distinguish the glasses the morereadily to the eye, I have painted the apparent parts of the glasses within side, every semitone white, and the other notes of the octave with the seven prismatic colours, viz. C, red; D, orange; E, yellow; F, green; G, blue; A, indigo; B, purple; and C, red again; - so that glasses of the same colour (the white excepted) are always octaves to each other.

This instrument is played upon, by sitting before the middle of the set of glasses as before the keys of a harpsichord, turning them with the foot, and wetting them now and then with a spunge aud clean water. The fingers should be first a little soaked in water, and quite free from all greasiness; a little fine chalk upon them is sometimes useful, to make them catch the glass and bring out the tone more readily. Both hands are used, by which means different parts are played together. - Observe, that the tones are best drawn out when the glasses turn from the ends of fingers, not when they turn to them.

The advantages of this instrument are, that its tones are incomparably sweet beyond those of any other; that they may be swelled and softened at pleasure by stronger or weaker pressures of the finger, and continued to any

length; and that the instrument, being once well tuned never again wants tuning.

In honour of your musical language, I have borrowed from it the name of this instrument, calling it the Ar monica.

With great esteem and respect, I am, etc.

B. FRANKLIN.

TO MR. OLIVER NEALE.

On the best Mediums for conveying Sound.

DEAR SIR,

July 20, 1762.

I have perused your paper on sound, and would freely mention to you, as you desire it, every thing that appeared to me to need correction: But nothing of that kind occurs to me, unless it be, where you speak of the air as the best niedium for conveying sound. Perhaps this is speaking rather too positively, if there be, as I think there are, some other mediums that will convey it farther and more readily. It is a well-known experiment, that the scratching of a pin, at one end of a long piece of timber, may be heard by an ear applied near the other end, though it could not be heard at the same distance through the air. And two stones being struck smartly together under water, the stroke may be heard at a greater distance by an ear also placed under water, than it can be heard through the air, I think I have heard it near a mile: how much farther it may be heard I know not; but suppose a great deal farther, because the sound did not seem faint, as if at a distance, like distant sounds through air, but smart and strong, and as if present just at the ear. — I wish you would repeat these experiments now you are upon the subject, and add your own observations. And if you were to repeat, with your naturally exact attention and observation, the common experiment of the bell in the exhausted receiver, possibly something new may occur to you, in considering,

-

that

1. Whether the experiment is not ambiguous; i. e. whether the gradual exhausting of the air, as it creates an increasing difference of pressure on the outside, may not occasion in the glass a difficulty of vibrating, renders it less fit to communicate to the air without, the vibrations that strike it from within; and the diminution of the sound arise from this cause, rather than from the diminution of the air?

2. Whether as the particles of air themselves are at a distance from each other, there must not be some medium

between them, proper for conveying sound since otherwise it would stop at the first particle?

3. Whether the great difference we experience in hearing sounds at a distance. when the wind blows towards us from the sonorous body, or towards that from us, can be well accounted for by adding to or subtracting from the swiftness of sound, the degree of swiftness that is in the wind at the time? The latter is so small in proportion, that it seems as if it could scarce produce any sensible effect, and yet the difference is very great. Does not this give some hint, as if there might be a subtle fluid, the conductor of sound, which moves at different times in different directions over the surface of the earth, and whose motion may perhaps be much swifter than that of the air in our strongest winds: and that, in passing through air, it may communicate that motion to the air which we call wind, though a motion in no degree so swift as its own?

4. It is somewhere related, that a pistol, fired on the top of an exceeding high mountain, made a noise like thunder in the valleys below. Perhaps this fact is not exactly related: but if it is, would not one imagine from it, that the rarer the air, the greater sound might be produced in it from the same cause?

5. Those balls of fire which are sometimes seen passing over a country, computed by philosophers to be often thirty miles high at least, sometimes burst at that height: the air must be exceeding rare there, and yet the explosion produces a sound that is heard at the distance, and for seventy miles round on the surface of the earth, so violent too as to shake buildings, and give an apprehension of an earthquake. Does not this look as if a rare atmosphere, almost a vacuum, was no bad conductor of sound?

I have not made up my own mind on these points, and only mention them for your consideration; knowing that every subject is the better for your haudling it.

With the greatest esteem, I am, etc.

B. FRANKLIN.

TO LORD KAIMS, AT EDINBURG. On the Harmony and Melody of the old Skotch Tunes.

June 2, 1765.

*** In my passage to America I read your excellent work, the Elements of Criticism, in which I found great entertainment. I only wished you had examined more

186

MELODY OF THE OLD SCOTCH TUNES.

fully the subject of music, and demonstrated that the pleasure artists feel in hearing much of that composed in the modern taste, is not the natural pleasure arising from melody or harmony of sounds, but of the same kind with the pleasure we feel on seeing the surprising feats of tumblers and rope-dancers, who execute difficult things. For my part I take this to be really the case, and suppose it the reason why those who are unpractised in music, and therefore unacquainted with those difffculties, have little or no pleasure in hearing this music. Many pieces of it are mere compositions of tricks. I have somecommon audience, times, at a concert. attended by a placed myself so as to see all their faces, and observed no signs of pleasure in them during the performance of a great part that was admired by the performers themselves; while a plain old Scotch tune, which they disdained and could scarcely be prevailed on to play, gave manifest and general delight. Give me leave, on this occasion, to extend a little the sense of your position, that "melody and harmony are separately agreeable, and in union delightful, and to give it as my opinion, that the reason why the Scotch tunes have lived so long, and will probably live for ever (if they escape being stifled in modern affected ornament) is merely this, that they are really compositions of melody and harmony united, or rather that their melody is harmony. I mean the simple tunes sung by a single voice. As this will appear paradoxical, 1 must explain my meaning. In common acceptation, indeed, only an agreeable succession of sounds is called melody, and only the co-existence of agreeable sounds, harmony. But since the memory is capable of retaining for some moments a perfect idea of the pitch of a past sound, so as to compare with it the pitch of a succeeding sound, and judge truly of their agreement or disagreement, there may and does arise from thence a sense of harmony between the present and past sounds, equally pleasing Now the conwith that between two present sounds.

struction of the old Scotch tunes is this, that almost every succeeding emphatical note is a third, a fifth, an octave, or in short some note that is in concord with the preceding note. Thirds are chiefly used, which are very pleasing concords. I use the word emphatical to distinguish those notes which have a stress laid on them in singing the tune. from the lighter connecting notes, that serve merely, like grammar articles in common speech, to tack the whole together.

That we have a most perfect idea of a sound just past, I might appeal to all acquainted with music, who know how easy it is to repeat a sound in the same pitch with one just heard. In tuning an instrument, a good ear can easily determine that two strings are in unison by sounding them separately, as by sounding them together; their disagreement is also as easily, I believe I may say more easily and better distinguished, when sounded separately;