they are a series of smaller interchangeable tubings, which extend in length as they descend in pitch, and set the instrument in different keys.  The mouthpiece is a funnel shaped tube of metal, by preference silver; and, in the horn, is exceptionally not cup shaped, but the reverse:  it tapers, as a cone, from three-quarters of an inch diameter to about a minimum of three-sixteenths of an inch, and is a quarter of an inch where the smaller end of the mouthpiece is inserted in the upper opening of the crook.  The first horn has a mouthpiece of rather less diameter than the second.  The peculiar mouthpiece and narrow tubing have very much to do with the soft voice-like tone quality of the horn.  For convenience of holding, the tubing is bent in a spiral form.  There is a tuning slide attached to the body, and, of late years, valves have been added to the horn, similar to those applied to the cornet and other wind instruments.  They have, to a considerable extent, superseded hand stopping, by which expedient the intonation could be altered a semitone or whole tone, by depression of the natural notes of the instrument.  In brass, or other instruments, the natural harmonics depend on the pressure of blowing; and the brass differs entirely from the wood wind, in this respect, that it is rare, or with poor effect, the lowest or fundamental note can be made to sound.  Stopping the horn is done by extending the open hand some way up the bore; there is half stopping and whole stopping, according to the interval, the half tone or whole tone required.  As may be imagined, the stopped notes are weak and dull compared with the open.  On the other hand, the tubing introduced for valves not being quite conformable in curve with the instrument, and hampered with indispensable joins, unless in the best form of modern valve, affects the smoothness of tone.  No doubt there has been of late years a great improvement in the manufacture of valves.  Many horns are still made with crooks covering an octave from B flat to B flat, 8 feet 6 inches to 17 feet; but most players now use only the F crook, and trust to the valves, rather than to change the crooks, so that we lose the fullness of sound of those below F. The natural horn was originally in D, but was not always restricted to that key; there have been horns for F, G, high A, and B flat.  This may, however, be said for the valve horn, that it does not limit or restrict composers in writing for the open or natural notes, which are always more beautiful in effect.

Valves were invented and first introduced in Prussia about A.D. 1815.  At first there were two, but there are now generally three.  In this country and France they are worked by pistons, which, when pressed down, give access for the air into channels or supplementary tubings on one side of the main bore, thus lengthening it by a tone for the first valve, a semitone for the second, and a tone and a semitone for the third.  When released by the finger, the