HARMONICA, or ARMOIVICA, is a name which Dr. Fanklin has given to a musical instrument constructed with drinking glasses. It is well known that a drinking glass yields a sweet tone, by passing a wet finger round its brim. Mr. Pockrich, of Ireland, was the first who thought of play ing tunes formed of these tones. He col lected a number of glasses of different sizes, fixed theM near each other on a ta ble, and tuned them by putting into them water, more or less, as each note re quired. Mr. Delaval made an instrument in imitation, and from this instrument Dr. Franklin took the hint of constructing his Artiionica. The glasses for this musical instrument are blown as nearly as possi ble in the form of hemispheres, having each an open neck or socket in the mid. dle. The thickness of the glass near the brim is about one tenth of an inch, increas ing towards the neck, which in the larg est glasses is about an inch deep, and an inch and a half wide within; but these dimensions lessen as the size of the glasses diminish, only observing that the neck of the smallest should not be shorter than half an inch. The diameter of the largest glass is nine inches, and that of the small est three inches : between these there are twenty-three different sizes, differing from each other a quarter of an inch in diameter. For making a single instru ment there should be at least six glasses blown of each size, and out of these thir ty-seven glasses (which are sufficient filr three octaves with all the semitones) may be found, that will either yield the note required, or one a little sharper, and fit ting so well into each other, as to taper regularly from the largest to the smallest. The glasses being chosen, and the note for which each glass is intended being marked upon it with a diamond, they are to be tuned, by diminishing the thickness of those that are too sharp, which is done by- grinding them round from the neck towards the brim ; comparing, by means of a well-tuned harpsichord, the tone drawn from the glass by your finger with the note you want, at, sounded by the corresponding string of the harpsichord. The largest glass in the instrument is G, a little below the reach of a common voice, and the highest G, including three com plete octaves ; and they are distinguished by painting ' the apparent parts of the glasses within side, every semitone white, and the other notes of the octavewith the seven prismatic colours ; so that glasses of the same colour (the white excepted) are always octaves to each other.' When the glasses are tuned, they are to be fixed on a round spindle of hard iron, an inch in diameter at the thickest end, and ta pering to a quarter of an inch at the small est. For this purpose the neck of each
glass is fitted with a cork, projecting a lit tle without the neck : these corks are per forated with holes of different diameters, according to the dimension of the spindle in that part of it where they are to be fix ed. The glasses are all placed within one another ; the largest on the biggest end of the spindle, with the neck outwards ; the next in size is put into the other, leav ing about an inch of its brim above the brim of the first ; and the others are put on in the same order. From these ex posed parts of each glass the tone is drawn, by laying a finger upon one of them as the spindle and glasses turn round. The spindle, thus prepared, is fix ed horizontally in the middle of a box, and made to turn on brass gudgeons at each end. A square shank comes from its thickest end through the box, on which shank a wheel is fixed by a screw : this will serve, like a fly, to make the motion equable, when the spindle is turned by the foot like a spinning-wheel. The wheel is eighteen inches in diameter, and con ceals near its circumference about twen ty-five pounds of lead, and may be made of mahogany. An ivory pin is fixed in the face of the wheel, about four inches from the axis ; over which is put the loop of the string that comes up from the move able step to give it motion. The box is about three feet long, eleven inches wide at the biggest end, and five inches at the smallest end ; it is made with a lid, which opens at the middle of its height, and turns up by back-hinges. The instrument, thus completed, stands on a neat frame with four legs. This instrument is played upon by sitting before it, as before the keys of a harpsichord, turning the spin dle with the foot, and wetting the glasses, now and then, with a sponge and clean water. The fingers should be first soak ed in water ; and rubbed occasionally with fine chalk, to make them catch the glass, and bring out the tone more rea dily. Different parts may be played to gether by using both hands ; and 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, says Dr. Franklin, are, that its tones are incomparably sweet be yond those of any other ; and that they may be swelled and softened at pleasure by stronger or weaker pressures of the finger ; and continued to any length : and, when it is once well tuned, it never again wants tuning. Franklin's Letters, &c.