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Stopped Diapasons, &c. ; but in some of the modern instruments, especially those that have to bear a severe climate, this class of pipe is not unfrequently to be found. The old builders, too, occasionally made the Stopped Diapason of metal; and the instances that remain to us of this class of work are extremely mellow and fluty in quality. Smith used them in many of his organs, as also did the Harrises, Crang and Hancock, and other old craftsmen. There was one by the elder Harris in the organ at Gloucester Cathedral (1670), though it has mysteriously disappeared within the last thirty years. A remarkably good specimen remains in a small organ at Boreham Church, Essex, which has been mis-labelled

B

D E

F

H

FIG. 58. VARIOUS FORMS OF METAL PIPES.

"Unison Wood." There is this distinction between the old Diapasons of this type and the modern instances, viz., that now-a-days a wooden stopper is placed within the tube (Fig. 58, c), whereas the old specimens are covered by a metal cap fixed over the top of the pipe (Fig. 58, D).

The

Conical pipes (Fig. 58, E) were not very frequent in old organs. German Spitzflöte and Gemshorn are of this shape. Smith introduced conical pipes for Gemshorns; one of his make still remains in the organ he erected at Tiverton. In modern work this pipe is more frequently adopted. The Spitzflöte in the Regent's Park organ is conical. Messrs.

Hill and Son have a stop of this form named the "Cone Gamba," which they frequently use in their organs.

Inverted cone-shaped pipes (Fig. 58, F) are to be found in every organ of any pretensions. Almost all the reeds are of this shape, viz., the Trumpet, Pausaune, Horn, Clarion, Bassoon, &c. Flue pipes are not so common of this outline. A German stop called "the Dolcan " is after this shape, and Hill and Son occasionally introduce such a stop into their work, but they are not general.

Conical pipes with bell (Fig. 58, G), are peculiar to English organs. These were introduced by the late Mr. Hill, who made a Cone Gamba in this form.

Inverted conical pipes with bell (Fig. 58, н), are used only for the Oboe stop in the reed work. As a rule the tubes of this register are of small scale, and if well voiced are delicate, and not unlike the instrument after which the stop is named. The old builders almost invariably made

their "Hautboys," as they were then labelled, of this shape, and some that still exist of their making are rich and refined in quality.

CHAPTER XVII.

Construction of Pipes.

To understand thoroughly the various parts of a pipe, it is essential to master the principles on which the sound depends, and to appreciate the several functions performed by each individual portion, in order that the desired result may be brought about.

It was seen that flue pipes were dependent for their sound on the vibrations within their bodies, and, going a step further, these vibrations are set up by others which occur at the mouth. The mouth itself, therefore, is only a means to an end, and is not essential to the sounding of a pipe per se. This is demonstrated by allowing a small stream of hydrogen to burn in an open tube; the combination of this gas with the oxygen of the atmosphere sets up a series of vibrations within the tube, which produce a musical sound in accordance with its length. In organ pipes, when the air is forced through the "wind-way," the stream is directed against the upper lip. This "sheet of wind," as it is termed, is under several influences. The air that comes out of the mouth of the pipe, in passing upwards, causes a draught underneath with an inward tendency; now, the sheet of wind from the wind-way is exposed to this from the outside, whereas the walls of the pipe guard it from the opposite direction, and therefore a varying pressure is caused, the air within being insufficient to counteract the inward draught, the sheet of wind gives way momentarily, but being the stronger, immediately supersedes, and thus a continual oscillation is set up, and is communicated to the column of air within the pipe. It must be distinctly remembered that the pipe itself does not vibrate. If it did, the calibre of its material would alter the pitch of the note produced; but such is not the case, the quality of tone and not the pitch being only affected by this circumstance.

An interesting exception to the above is observed in connection with four-sided pipes, that whereas in these the backs and fronts remain

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motionless, the sides are subject to considerable vibration. The reason that a closed pipe produces a tone equal to that expected from an open one twice its length, is that the column of air within the body has to pass up to the top and down again before it can make its exit, and is therefore in reality as long again as the pipe which contains it.

It is found in organ pipes that if they are made very narrow in proportion to their width of mouth they do not speak the note apparently natural to the length of body, but the octave, or some other " harmonic," the reason of which is that the vibrations at the mouth are too rapid to correspond with those that the tube requires; the column of vibrating air, therefore, at once splits into two divisions, and renders the note natural to the lengths into which it has been forced to divide.

This is again exemplified if a pipe of ordinary dimensions is overblown, the tendency is then to increase the velocity of vibrations at the mouth, and an harmonic sound, consequent on division of the column, is the result. M. Cavaille Coll has introduced harmonic stops into the organ and utilised this law. He accomplished the perfect and rapid speech necessary by boring a small hole about the middle of the body of narrow scale pipes, constructed for the purpose; an equal division of the column within was the result, and the desired octave was produced. It is due to M. Coll to give him all praise for his invention, and his practical application thereof, but many years previously Sir Frederick Ouseley had worked out the idea and written privately on the subject.

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FIG. 59. THE LANGUID.

In point of fact, all flue pipes are constructed on the same principle, and have the same component parts, but the differences of shape and material have led to a distinction in nomenclature. Besides the "body," 'mouth," and "foot" described in a previous chapter, a metal flue pipe contains a "6 languid" or "language" (Fig. 59); this is a flat piece of metal that is placed immediately over the foot, within the mouth; it is soldered firmly by its sides and back, having no other support; it is of thicker calibre than any other portion of the pipe, its solidity and stability being of the utmost importance. It presents in front a straight edge, which is parallel to the lips of the body and foot, and this edge forms the back boundary of the "wind-way," which is the opening allowed between the languid and the lower lip. Any movement of the languid would at once alter the direction of the sheet of wind, and seriously affect or altogether stop the speech of the pipe. This is why the strength of the languid is of such great importance.

Metal flue pipes are often furnished with " 'ears," and in the case

of some stopped and half-stopped pipes they assume considerable size and importance. They are said to keep the wind together, as it were, and direct it more surely against the upper lip. They are therefore useful where a pipe may be "cut high" and there is any fear that the wind may not "reach." In some cases, especially in old work, pipes are tuned by long ears made for that purpose; in ordinary open flue pipes they are

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small, and add a neatness and general finish to the appearance of the stops in sight.

Wooden flue pipes are made on precisely the same principle as are those of metal. But their shape has necessitated some modification of particular parts, and hence a distinct nomenclature has sprung up in relation to these pipes. The "body" is a rectangular tube, the cross section of which is usually oblong; at the lower end it is closed by the

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