especially light wind, and therefore, where this is not required, a compound containing some proportion of lead is used. Spotted metal gives a full round tone, and is superior therefore in this respect to tin, at any rate, for the large scale flue work. Lead wants the brilliancy and ring of the foregoing materials, and is somewhat dull. Other mixtures may be said to vary according to their composition. Zinc is only used for the larger pipes, and when well voiced possesses a very grand full quality of tone, and is in every way fitted to the purpose to which it is applied. The thickness of the metal has also some influence on tone, and it is found that the thicker the substance of a pipe is made the more round and satisfying is the effect produced. Good or bad pipe material can be detected in a number of ways. The experienced eye needs little to assist it. Dark blue looking pipes usually have a preponderance of lead. Lead pipes, again, when tapped with the nail give a dull sound; they will soil the hand or a white handkerchief if rubbed, and they are easily scratched. The reverse of all this is noticed in tin work, and spotted metal can never be mistaken. A great deal depends upon the choice of metal in building organs. We repeat that the voicer holds the tone and the speech almost entirely in his hands, but durability and actual lasting worth are dependent on the metal chosen. Spotted metal is always advisable, and we think that it is a mistake to imagine that much is gained by having a higher percentage of tin in metal work than is here obtained, except for special registers, as choir salicets, orchestral oboes, gambas, &c., and stops of sharp intonation. For an accurate description of the way in which the metal is worked up we must refer the reader to larger works on the subject. Dom Bedos enters fully into this subject, and gives some very interesting engravings, which show us that little alteration has been effected since his day. Suffice it to say here that the metal is cast in shallow troughs into sheets a little thicker than the actual calibre required, and having been planed smooth after cooling, is cut into strips of a suitable width. The way in which wood should be prepared was described in the first chapter of this division, page 40. CHAPTER XVI. Different Forms of Organ Pipes. ORGAN pipes are divided into two great classes, viz., "flue pipes" and "reeds." Flue or mouth pipes are dependent for their sound on the vibration of air within their body or tube. The greater the number of these vibrations the more acute is the sound produced, and conversely. The celerity of vibrations depends upon the length of the column of air within the pipe.* One column half the length of another makes twice the number of vibrations in the same time, and one column double the length of another makes half the number of vibrations in a like period, i.e., provided the diameters and weight of wind, &c., are equal. The effect of "stopping a pipe," or closing the upper end, is to decrease the number of vibrations by half, so that a stopped pipe of given length produces the same sound as would one twice its length if The lowest note appreciable by the human ear as a musical sound is produced by sixteen vibrations in one second, and is the note given by the 32ft. open pipe, viz., c c cc; the highest note we can distinguish is produced by sixteen thousand three hundred and eighty-four vibrations per second, and its musical name would be c'. Some idea of its pitch may be gathered from the fact that it is four octaves above the highest note of the foundation tone of the Regent's Park organ, or no less than ten octaves above the lowest note c c c c. open. The vibrations are set up in organ pipes by forcing the wind through a narrow passage or "wind way" behind the "lower lip" (A, Fig. 55), so that on emerging the stream is split by the " upper lip," B, some going inside the pipe and the rest escaping. The opening between the lips of a pipe is called "the mouth;" that portion below the mouth is called "the foot," c, and all above "the body," D. The reed pipes, on *This is not absolutely the case, but practically it comes to this as far as organ pipes generally are concerned. the other hand, do not depend upon the length of their tube for the pitch of the sound they produce, but upon the vibration of a metal tongue or "reed," a further description of which, as also of the individual parts of flue pipes, will be found in the next chapter. Pipes have varied in design and shape ever since a distinction in tone or calibre of sound became appreciated or attainable; and by reference to old works on the subject we find that the early builders were fully alive to the advantages gained by variation of form, which affected the tone of the registers they employed. The engravings --d FIG. 55. METAL FLUE FIG. 56. OBSOLETE FORMS (DOM BEDOS). in the work by Dom Bedos show us that the main features of the stops then known and used differed in no very marked degree from similar ones of the present day. Fig. 56, A, is a reduced copy of a Stopped Diapason taken from the above-mentioned work, and it points to a care and finish that would bear comparison with modern achievements. The German builders of the last century were given to constructing pipes, especially reeds, of very curious form, of which в and c (Fig. 56) are specimens ; B represents an Apple or Button Regal, a reed stop now no longer used, the pipes of which were very short; c is a "Bear's Pipe," described K as a reed of soft intonation." The tubes varied in form throughout its compass, and some of them are said to have resembled in shape the Vox Humana in the Temple organ, by Father Smith. In the present day pipes may be divided into the following groups, having reference to outline : There are a few uncommon pipes which escape this list, but for all practical purposes it is sufficient. For convenience of description we shall follow the order above taken. Four-sided pipes are invariably of wood, and are, as the table shows, divided into three groups-open, half-stopped, and stopped. Open pipes of four sides (Fig. 57, A) are to be found in almost any organ; in small instruments they frequently form the bass of the Open Diapason, and some of the flute work is constructed of these, as also is the Claribella. The Open Diapason, 16ft. on the pedal, is always of this shape when made of wood. Half-stopped four-sided pipes (Fig. 57, B) are by no means so common as the foregoing. They are closed at the top by a stopper, through which a small hole is bored, or a tube inserted. Some flutes are of this description, and the treble of the Stopped Diapason is occasionally so made, but the practice is not extended to the larger pipes in any instance. Stopped pipes of four sides (Fig. 57, c) are to be seen in all old organs, and in nine-tenths of the modern ones. They resemble the open in shape, but are closed at the top by a plug, c. The Stopped Diapason is usually of this kind, and in the smaller instruments the bass of the Dulciana, Viol-di-Gamba, or any soft stop is often continued below tenor c with these pipes. The Bourdon is always made after this pattern, except in a few modern instruments, where it is of metal. The Double Diapason, unless otherwise specified, is also always made of this shape. Three-sided pipes are comparatively rare, and appear to have no special advantage over those of four sides. Messrs. Forster and Andrews have placed one in the organ they erected at Halifax. Pyramidal pipes (Fig. 57, D) occur as the bass portion of the conical stops, as, for instance, in the case of the Gemshorn. Inverted pyramidal pipes (Fig. 57, E) are much used for the large reeds, especially in pedal organs, where the tubes of the 16ft. and 32ft. are usually made of this shape when not of metal. The Bombarde in the organ at the Pro-Cathedral, Kensington, is of this description. Sometimes 8ft. reeds are so constructed, an instance of which occurs in the organ built by the late Mr. Hill for the Wesleyan Chapel, Poplar, where a Bassoon on the choir is of this character. Cylindrical pipes form the staple of all organs whatsoever. They are marked in the table as being of wood and metal. This is so in point of fact, though we may dismiss the former by saying that now-a-days, only rarely in Germany is a delicate kind of flute made of wood in this shape. Open cylindrical pipes (Fig. 58, A) go to make up by far the majority of stops on an ordinary organ. The Open Diapason, Principal, Fifteenth, and all Mixtures and mutation stops are of this type. The Keraulophon, Dulciana, harmonic stops, and some of the more delicate reeds, as, for instance, the Vox Humana and Clarionet, also belong to this group. Half-stopped metal pipes (Fig. 58, в) are not uncommon in English organs. A small tube is made to pass through the ordinary stopper. The French stop, “Flute à chèminée,” takes its name from this peculiarity in make. Some of the old metal flutes are also found of this form. Closed cylindrical pipes (Fig. 58, c) are not nearly so common, for until recently builders have used wood in preference to metal for the |