Introduction.--The clear tones of a viol or bass viol are generally admitted to be more melodious than those produced by other kinds of instruments, and many have expressed a desire to see an instrument so constructed as to be played with keys, like the organ or piano forte, and give the tones of the violin. This is the character of the instrument here introduced. It is elegant in appearance; occupies less than half the space of a piano forte, and is so light and portable that a lady-performer may readily place it before her, and thus avoid the necessity,--unpleasant to all parties,--of turning her back on the company. We do not say that an instrument of this kind has been as yet constructed complete: but the principle has been proved, and it may, and probably will be soon, offered to the public, at a cost not exceeding sixty dollars.

Explanation.--In the engraving, a side view elevation only is represented, showing only one string and one key of a series of twenty or more of each. The body of the machine A B, is a light hollow chest about three feet square and six inches deep, supported by four posts or legs with castors. Two bridges, C and D, extend across the breadth of the chest. The bridge D is supported by a cleat, E, in which is inserted the pin F, to which is attached one end of the string C D F. The other end of the string is simply attached to the bridge C. A key-lever, G H, passes through the bridge, and is mounted on a pivot therein. The front end of the key (G) is held in its ordinary position by a small spring thereunder, and may be easily depressed by the finger of the performer: the other end of the key serves as the bearing of the pivot of a delicate arbor, the opposite pivot of which has its bearing in the bridge D. On the front end of this arbor is a wheel three-fourths of an inch in diameter, with its periphery smooth, and polished with rosin, or rosin varnish; and so adjusted, that by the depression of the key, this wheel is brought up in contact with the string, whereby, if in motion rotarily, a full sound is produced, as if a violin bow was drawn across the string. On the other end of the arbor is a grooved pulley, over which passes a silken cord, which also passes round a delicate band-wheel, I, below, and by which, motion is communicated to the arbor and sounding wheel. The band-wheel is mounted on a shaft, I J, which has its bearings in two small head blocks which project from two crossbars: and from the block J is suspended a vertical rod, to the bottom of which is attached a treadle, K L, and from which a curved ratch, L M, extends upward and takes to a small ratchet on the shaft I J; so that, by the horizontal motion of the treadle, the motion is communicated to the wheel, &c. The teeth of the ratch and ratchet have so gentle an inclination on one side of each, that although the ratch applies force to the ratchet in the upward direction, they slide freely over in their return. It may be understood that the machine is to have two treadles and two ratches, which move forward alternately: and that twenty or more arbors, pulleys, strings and keys are arranged in series, although only one of each is represented in the engraving. The cord applies to each pulley in the series, by passing over the first, under the second, and over the third, and so on, descending from the last of the series to the band-wheel. Each arbor is placed directly under its respective string, and it is also proposed to place moveable stops under the strings, at equal distances from the key bridge, and to regulate the tones by adjusting the stops, without depending on the pins at the ends for that purpose. We shall employ a competent mechanic to construct one or more of these instruments as soon as convenient, and give due notice accordingly.