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.

of

My largest glass is G, a little below the reach of a common voice, and my highest G, including three compleat octaves.---To distinguish the glasses the more readily to the eye, I have painted the apparent parts 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,

6

sichord, turning them with the foot, and wetting them now and then with a spunge and 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 the 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 Armonica.

With great esteem and respect, I am, &c.

B. FRANKLIN

TO A FRIEND*.

Respecting 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

* Mr. Oliver Neave. Editor.

appeared

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 medium 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 may be have heard it near a mile; how much farther it 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,

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, that 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

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 substracting 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 that 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

VOL. II.

as

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 handling it.

With the greatest esteem, I am, &c.

B. FRANKLIN.

TO LORD KAIMS, AT EDINBURGH.

On the Harmony and Melody of the old Scotch 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 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 difficulties, have little or no pleasure in hearing this music. Many pieces of it are mere compositions of tricks. I have sometimes, at a concert, attended by a common audience, placed myself so as to see all their faces, and observed no signs of pleasure in them during

the