l'glloir•s of the simplest form are con structed after the ma ruler of the smith's bellows, i.e. pump work. A distinction is made between horizontal and diagonal bel lows. (ff whatever shape o• f um they are hut one thing is necessary. that they he ample for the full organ. Automatic organ-blowing engines or are now common. the manufacture of which is a trade by itself. The rule has boat laid down that a water pressure of at least thirty five pounds to the square inch is necessary for blowing by water. In this method two pairs of bellows are required. one pair (which is for the exclusive operation of the ei>ginel having square rising feeders: and an ordinary waste valve, and the other pair toeing specially provided with feeders so that in ease of failure of the water or engine the lid lows may be blown by hand. Electric and gas en gines are not quite so eeoinonical. and suffer in comparison with water power from the fact that the electric engine is subject to disarrangement. and the gas engine is somewhat noisy by reason of the explosion:.
S01111(1b0(1)%1S and 11'111(1 (41( NiS are required to be of sufficient length and width to give the pipes plenty of speaking room. The wind chest is an airtight box or chamber having channels above the valves or pallets. one for each note. In connection with the wind chest or suundboard is the slider. When the performer draws the holes in the slide correspond to the holes in the table and upper board, and thus enable the wind to pass from the channels to the pipes. When the stop is returned, the slide is moved so that the holes do not corre spond, and the plain surface close, the channels to the pipes. Valve pallets are about an inch in thickness and from eleven to sixteen inches in length. All the spaces between the lower edges of the partitions of the soundboard except those which the valves cover are packed with filling, and each valve is maintained in its place by a steel spring. When the valve is opened to admit the wind to a pipe it is pulled down about half an inch at one end, while the other end is held in place by a pin. The valves in the wind chests are worked by a mechanism which is connected with the keys.
The key action deals with the entire process of causing a pipe to speak, the simplest method of which perhaps is the lever or fan frame move ment when the wind chest is built on semitonal principles; upright rods (stickers) are placed upon the inside ends of the keys, and the tops of these are inserted in one end of the levers. which
are arranged perpendicularly over each respective key, the other ends converging under the pull down wires of the wind chest. Should these wires be some distance from the keys, tracker action is used. Trackers are thin strips of wood capable of sustaining weight longitudinally; should the trackers be very long, guides are provided for their support. Thus when the key is depressed it causes an almost instantaneous action whereby the wind is permitted to reach the pipe and cause it to speak. The compass on an organ manual is usually from ('C to CI or A, although it is better extended to C, as is sometimes done, thus completing the live octaves. This latter is especially desirable where the pedal organ ranges from CC'C to P (30 notes). The names of the more important stops will be found discussed under their own titles. See also 1TAnm ox l'M lEi.orwoN ; Vole) NG ; MENT; TREM ULANT ; TUNING.
BIBLioGRA RD v, Hint( or. Organ. Construction (London. ; Labe°. The Organ and Its hos iers (Boston, 1903) ; Matthews, .1 Handbook of the Organ (London, 1897) ; Frenzel. Dic rgcl and ihre .11vistu• (Dresden. 1884) ; Zienmer, Orgcl ( Quedl Mat rg, ]Simi) : Dixon. Practical Organ Building (London. ; Stainer, The Organ (ih., 1S77): 11i11. The Organ ('uses and Organs of the Middle Ages and Renaissance fib., 18911; Hopkins, "The English \le• dheval Church Organ," in The Archwological Journal, vol. xiv. 1Stiti); Elliston, Organs and Toning (ib., 1894) Ilopkins, The Organ, Its History and Construction (3d ed., ib., 1S771: Sutton, Church Organs, Their Position and Construction (ib.. I?=.721 ; War man, The Organ: Its Compass, Ta Ida t u re, and Phort and Incomplete Octarcs (ib., [SO); Seidel, Die Orgel and ihr Boa (4th ed., Leipzig, ISS7; Eng. trans., London, 1SS5) Peg chard, Leg prcmie'rcs applications de aux grandes orgucs (Paris, 1890) ; and for a bibliography of the organ, consult Notes and Q uerics ( London, 1890).