We now come to the trombones, grand, sonorous tubes, which, existing in three or four sizes since the sixteenth century, are among the most potent additions on occasion to the full orchestra. Their treble can be regarded as the English slide trumpet, but it is not exactly so. There appears to have been as late as Bach a soprano trombone, and it is figured by Virdung, A.D. 1511, as no larger than the field trumpet. The trumpet is not on so large a caliber, and in the seventeenth century had its own family of two clarinos and three tubas. The old English name of the trombone is sackbut. The old wooden cornet, or German zinke, an obsolete, cupped mouthpiece instrument, the real bass of which, according to family, is the now obsolete serpent, was used in the sixteenth and seventeenth centuries as the treble instrument in combination with alto, tenor, and bass trombones. The leading features of the trumpet are also found, as already inferred, in the trombone; there is the cupped mouthpiece, the cylindrical tubing, and, finally, a gradual increase in diameter to the bell. The slide used for the trumpet appears for four centuries, and probably longer, in the well known construction of the trombone. In this instrument it consists of two cylindrical tubes parallel with each other, upon which two other tubes communicating by a pipe at their lower ends curved in a half circle glide without loss of air. The mouthpiece is fitted to an upper end, and a bell to a lower end of the slide. When the slide is closed, the instrument is at its highest pitch, and as the column of air is lengthened by drawing the slide out, the pitch is lowered. By this contrivance a complete chromatic scale can be obtained, and as the determination of the notes it produces is by ear, we have in it the only wind instrument that can compare in accuracy with stringed instruments. The player holds a cross bar between the two lengths of the instrument, which enables him to lengthen or shorten the slide at pleasure, and in the bass trombone, as the stretch would be too great for the length of a man's arm, a jointed handle is attached to the cross bar. The player has seven positions, each a semitone apart for elongation, and each note has its own system of harmonics, but in practice he only occasionally goes beyond the fifth. The present trombones are the alto in E flat descending to A in the seventh position; the tenor in B flat descending to E; the bass in F descending to B, and a higher bass in G descending to C sharp. Wagner, who has made several important innovations in writing for bass brass instruments, requires an octave bass trombone in B flat; an octave lower than the tenor one, in the "Nibelungen." The fundamental tones of the trombone are called "pedal" notes. They are difficult to get and less valuable than harmonics because, in all wind instruments, notes produced by overblowing are richer than the fundamental notes in tone quality.