ORGAN. Having, under the article MusicAL inztrunCC7as, given a pretty full account of this instrument, we shall here only give a description, with figures, of the barrel-organ. See Plate I. Barrel Organ, and Plate IL parts of ditto.
The barrel-organ is generally portable, and is so contrived, that the same action of the hand, which turns the barrel, sup plies the wind, by giving motion to the bellows : it consists of three principal parts : 1. The pipes, by which the sound is produced. 2. The bellows, supplying them with air. 3. The barrel and keys, by which the pipes are sounded at pro per intervals. The pipes are of two kinds, of metal and of wood : the wood en ones are a square trunk of deal wood, A II, (fig. 5) closed at one end by a plug of wood, D, and at the other by a piece of wood, E, containing a crooked pas sage to bring air to the pipe, through the short tube, F ; a is a piece of oak board, glued to the block E, and hollowed out to communicate with the crooked passage in it, and leaving a small crack, between it and the edge of the block, E, through which the air issues in one continued stream ; in its passage it is divided by the edge of one side of the trunk, A, which is cut as sharp as possible for that purpose, and which is exactly in the same line with the orifice whence the air is emitted.
The sound is produced by the vibra tion of the air which is contained in the trunk, A, and by increasing or diminish ing the length of the pipe, the tone is altered at pleasure, to bring it to the pro per note it is to perform when placed in the instrument : this is done by sliding the plug, D, up or down in the pipe.
A metal pipe, a section of which is shown in fig. 6, is nearly the same in its operation, though different in its con struction. It is a cylindric tube, of a mixture of lead and tin ; A B, (fig. 6) open at one end, and nearly closed at the other by a lump of the same metal, E, which is circular for about two-thirds round, and fits the end of the pipe ; the other third is a straight edge : the upper edge of the conical pipe, F, is bent to be parallel to this, and thus forms a small cleft similar to the wooden one, for the passage of the air, the lower edge of the cylindrical pipe, A 13, is bent into the line of the cleft and cut sharp, to divide the current of air; these pipes are open at top, and are brought to tune by bend ing the pipe at the top, and thus altering its bulk : a is a piece of metal, called the ear, soldered upon the pipe at each end of the cleft, to prevent the stream of air being dispersed before it meets the sharp edge of the pipe, B A ; in the small pipes this is not applied.
The bellows of the organ are double, as shewn in fig. 1, Plate I; that is, they are two distinct pairs, E, F, connected together at their hinge ; so that when one is opening, and filling with air, the other is forcing its air out into the regu lator, D; the bellows receive their mo tion by a rod, d, from a crank, a, on a spindle which comes through the box, in which the machine is enclosed, and has a handle on it by which it is turned. The regulator, D, is exactly similar to another pair of bellows, and is filled with air from the bellows, E F, below it, through two valves in the bottom board over the bellows ; from this regulator the air pro ceeds through the passage, b ef, (seen better in the section), fig. 2, &c.
Fig. 2, Plate I, to a long trunk, g, go ing under the pipes called the air-chest, which communicates with them by a small valve, h, under each, it is kept shut by a small wire spring, and is opened by a wire fixed to the end of a rod, G ; above the valve, the passage enlarges, and goes under two small wooden sliders or stops, n m, and from thence in two dis tinct passages to the wooden and metal pipes, N M.
The air-chest, g, is common to all the pipes, and each pair (of wooden and me tal pipes) has a valve, Is, and spring to themselves; the small passage above each valve belongs to each pair of pipes, and has no connection with the other ; the two stops belong to all the pipes ; m, to the metal, and 71, to the wooden ones ; they are long slips of wood drilled with so many holes as there are pipes, and at the same intervals, (the disposition of the pipes is shown in fig. 3, which is a plan of the whole instrument put together) ; so that when the holes are over the pas sages, the air has free communication from the valve to the pipes ; but when the stops are drawn out, the interval be tween each hole applies itself to the holes under the pipes, and thus stops the pas sages.