but should it be already out, pressing the pedal closes the slider and shuts off the pipes.

Fig. 38 shows the mechanism: s is the end of the sound-board, c is a slide, and J a fixed guide. The pedal is connected at i by any suitable arrangement of rods, levers, &c., according to circumstances. The depression of the pedal causes the rod F to rise, and its upper end, engaging in one of the hollows of the cam A, rocks the latter on its centre B, and moves the slide c; on the release of the pedal, the rod F, which if necessary is weighted, drops out of f, and the roller & descending the incline presented by the wire E, the pedal returns to its normal condition. The next depression of the pedal will cause the rod F to engage in the other hollow of the cam, restoring the slide to its original position. In this arrangement each commutation pedal may be connected to a single slide or to several, as is convenient. If it be desired, the mechanism may be arranged to act on two sliders, so as to reverse them under any circumstances, or it may be arranged so that, if one slide has been moved by hand without the other, the depression of the pedal will move the other in the same direction; a subsequent movement reversing both simultaneously. The ordinary draw-stop action may be retained and connected to the slider as usual, or to the cam, as seen at m or n in Fig. 38.

In using these pedals for the speaking stops of small one-manual organs, the advantage gained is, that by reason of the very slight pressure required to alter the slide, the stops can be quickly regulated without the removal of the hands from the keys. It is needless to point out how useful such an arrangement may be for the command of couplers or heavy pedal reeds on large instruments, where the hands can seldom be spared.

The application of the pneumatic power-bellows to the sliders was naturally suggested on its successful interference on behalf of the key action; and a moment's consideration will show that it is more than ever of use in moving the tight sliders, and dispensing with the heavy action that would make the drawing of every stop a matter of considerable exertion. The power-bellows are actuated either by a train of mechanical action, by electro-magnets, or by means of a contrivance which may be termed the "tubular transmission." The first arrangement is purely pneumatic, the second is compound electric and pneumatic, and the third is pneumatic in its principle.

In the tubular arrangement the stop-knob at the keys moves a peculiar kind of double action valve, which places a tube, in connection with the pneumatic power-bellows at the end of the slider, under the influence of either exhaust or pressure, according to whether it is

drawn out or pushed in, thus obtaining the alteration in the position of the slider. The transmission through the tube, which is merely a leaden gas pipe, can be effected to any distance, and in this arrangement all the complications attending mechanical movements are dispensed with, and an enormous saving of space is the result.

The simple pneumatic draw-stop action is accomplished by fixing a power-bellows of sufficient size on a vertical board, as shown in Fig. 39. The slide to be acted on is connected by a lever, or other mechanical

arrangement, to the moving part of the power-bellows. In the figure it will be seen that three chambers, A, B, C, are fixed on the reverse side of the vertical table, T. These chambers communicate with each other by two holes in the partitions between them, but this communication is determined by the position of a double action valve, consisting of a rod, r, and two discs, d d, with suitable seats on the partitions. The upper chamber is supplied with a pressure of air from bellows connected with it by a trunk not shown in the drawing. The other chamber,

c, has the air exhausted from it by any convenient means; the middle chamber, B, communicates with the interior of the power-bellows, P. When the double-action valve rod, r, is pulled down it removes one disc, d, from its seat on the partition of the supply chamber, A, and closes the hole in the exhaust chamber, c, thereby allowing the compressed air to pass through the chamber, c, into the power-bellows, P, and thus through the rod, R, to move the soundboard slide one way. On reversing the valve the wind from the supply chamber, A, is cut off, and communica

FIG. 39. THE PNEUMATIC DRAW STOP ACTION.

tion with the exhaust chamber, c, is established, thereby causing the power-bellows, P, to collapse, as shown in Fig. 39, and move the rod, R, and the soundboard slide in the reverse direction. This double-action valve can be commanded at the console either by a mechanical arrangement of levers, conrecting-rods, &c., by the application of electricity and electro-magnets, as also by the tubular action mentioned above. If electricity is employed, it is necessary for the sake of economy to introduce intermediate or accessory power-bellows. The

accessory bellows shown at p, in Fig. 39, is supplied by a separate discvalve, v, from the supply chamber, s, in connection with the main powerbellows, and may be actuated by two electro-magnets, E E.

The means by which the two distinct positions of the double-action valve of the main power-bellows is insured is as follows: The two electromagnets, E E, are placed in such a position that their armatures can act on the rod, w, carrying the disc-valve, v, that admits compressed air to, and discharges it from, the accessory power-bellows, p.

These

FIG. 40. THE DOUBLE BELLOWS DRAW STOP.

accessory bellows are connected to the rod, r, of the main doubleaction valve which actuates the main power-bellows that moves the slide through the rod, R. Thus, by moving a draw-stop knob at the keys one way a contact is made which completes an electric circuit, and produces a current of electricity which actuates one electro-magnet, E, and closes the escape valve of the accessory bellows, p, and at the same time opens the supply valve which allows the compressed air from the chamber, s, to inflate the accessory bellows, and pull the rod, r, of

the main double-action valve one way. On moving the stop-knob at the keys in the reverse direction a contact is made which actuates the other magnet, E, and thereby alters the position of the disc-valve, v, of the accessory bellows, p, cuts off the supply, and allows the air to escape from the bellows into the atmosphere. The accessory bellows will then collapse and reverse the position of the main double-action valve.

Fig. 40 is a modification of the above, two pneumatic power-bellows, P P, being employed in combination. These two bellows, P P, are adapted to the two vertical boards, T T, between which are arranged the compressed air and exhaust chambers and their valves. In this instance the bellows are worked on the exhaust principle; B is the exhaust chamber from which the air is exhausted in any convenient manner; dd are valves for connecting the chamber, B, with the chambers, A C, which are in communication with the pneumatic bellows, PP. The valves, d d, are worked by means of the accessory bellows, p, as in the former instance, and the rod, R, of the draw-stop slide is shown in the figure as having been drawn over to the right. Now, if the electro-magnet, E, is put in action, it will attract its armature, and draw down the valve rod, w, cut off the supply of compressed air to the bellows, p, and at the same time open the communication through the lower valve, v, with the atmosphere. The bellows, P, will then collapse, draw down the rod and close the top valves, d d, at the same time opening the bottom ones. The air from the bellows, P, will then rush into the exhaust chamber, B, the bellows will collapse, and thereby push the slider-rod, R, in the opposite direction and at the same time open the other bellows, P, which will be inflated from the chamber, c, which is in communication with the atmosphere.