8. The _hand_ or _barrel organ_ consists of a moveable cylinder, on which, by means of wires, pins, and staples, are marked the tunes which it is intended to perform. These pins and staples, by the revolution of the barrel, act upon the keys within, and give admission to the wind from the bellows to the pipes. The hand organ is so contrived that the revolution of the barrel gives motion to the bellows. 9. There are several instruments belonging to the class of _horns_, all of which are made of brass or silver. Those of the latter kind of metal are by far the softest in tone, but brass is the material most commonly employed. The chief instruments belonging to this class are the trumpet, the French horn, the bugle, the Kent bugle, the trombone, and the bass-horn. The _serpent_ seems to be the connecting link between the trumpet and the flute. 10. The instruments classed with the flute, are the common flutes of various keys, German flutes, and several kinds of flageolets. Nearly allied to these are the clarionet, the hautboy, and bassoon. The breath is applied to the flageolet through an ivory tube at the end; and, in the three last named instruments, a thin reed, capable of a free vibration, is a part of the mouth-piece. 11. Of the instruments which produce musical sounds by the vibration of strings, there are a great number, of which the following are the principal;--the lyre, the harp, the guitar, the lute, the dulcimer, the harpsichord, the spinnet, the piano-forte, the violin, the violincello, and the base-viol. The strings of the three last are agitated with a bow; but those of this class first mentioned, are vibrated by the thumb and fingers, by some little instrument held in the hand, or by little hammers, moved by keys, as in the piano-forte. 12. The _piano-forte_ is said to be the invention of Gottlieb Schroder, of Hohenstein, in Saxony, born in Dresden, about the year 1717. Before the introduction of this instrument, the clavichord, harpsichord, and spinnet, supplied its place. On all of these instruments complete harmony can be produced by a single performer, and the most difficult series of tones can be executed with rapidity, by means of a simple mechanism. 13. The _piano-forte_ has been gradually improved, until it has become one of the most elegant instruments in the whole compass of musical practice. In firmness and strength of tone, the English piano-fortes formerly surpassed all others; but, within a few years, they have been equalled, and in some respects excelled, by those of American workmanship. The manufacture of this instrument constitutes the most extensive branch of musical instrument-making.