Buttons. Round nuts of old and thick leather, or latterly of a composition into which gutta-percha enters, pierced at their centre to receive the tapped part of the wire.
Cloths. Little discs of woollen cloth, mostly red, used as mufflers to prevent the rattling noise of wood against wood, or metal against metal.
Roller. An axis or shaft of light wood (but in certain cases of iron), turning easily on two wires as pivots, which enter holes in studs fixed firmly. The roller has two (or more) arms, 2 or 3 inches long, projecting from it, generally near its ends. It is plain that any motion given to the roller by acting on one of these arms will be transmitted to the other arm. Rollers are in sets, like backfalls and squares, and are arranged symmetrically on a board called a roller-board (Fig. 31).
The nine articles just described are all brought together in the action of an organ, even of a simple kind. We shall endeavour in this chapter to show how they are combined in ordinary circumstances, involving no peculiar complications.
A simple and rudimentary example of the principle underlying all systems of organ-action may be seen in Fig. 32. a b is the key-board, in which each key (as always in England) is balanced on a pin-rail near its centre, and has a pin, c, passing through a little mortice cut in it, while another pin, d, out of sight, near its fore end, keeps it in its place, parallel to its fellows. At the tail of the key, e is a sticker, having a wire thrust into each of its ends, and projecting about 1 inch; one of these wires is inserted in a small hole drilled in the key-tail, and conical beneath, or cut into a little mortice. A "cloth" is slipped upon the wire to prevent the end of the sticker from rattling upon the key-tail. The upper wire of the sticker slips into a similar hole (a cloth interposed as before) in the end of f, a backfall working in its bridge, g. The other end of f is connected at once to the pull-down of the pallet by a tapped wire and button. Clearly, if a finger is placed upon the key, its hinder end will rise and will push up the back end of the backfall, which will draw down the pallet; and by simply reversing the position of the backfalls as shown in the cut, we may pull down the pallets in the wind-chest when placed under the back of the sound-board.
Fig. 31.
If, then, we have fifty-four keys in the manual, a repetition of this simple apparatus fifty-four times will be requisite to bring every pallet, with the pipes controlled by it, under the command of the player.
