640 THE POPULAR SCIENCE MONTHLY. 



f erred to — working tliem by the feet, the blowers holding on. to a 

 rigid transverse bar as they moved along the row (the bellows de- 

 scribed by the authority named numbered twenty, and were oper- 

 ated by two men)— was, however, known a thousand years previous, 

 in Constantinojjle. Passing over incidental contributions to that 

 department, it is only necessary to point out that the demands 

 upon the wind became so great in time that it was deemed neces- 

 sary to introduce mechanical means for supplying and regulating 

 the supply required. A hydraulic engine, invented by Joy and 

 Holt, of Middleborough, England, though defective in some re- 

 spects, was the first thing found to answer the purpose. Next 

 came a water-moter, invented by Thomas Duncan, which met 

 with some favor. Latterly, gas and electricity have been applied 

 with much success, and in the operation of the most comprehen- 

 sive organs little difficulty is experienced at present in supplying 

 and regulating the stock of wind required. 



When the organ-builder increased the compass of the instru- 

 ment and its effects, the perfecting of the key movement, the 

 invention of the draw-stop action for controlling the use of the 

 various tiers of pipes, the introduction of composition pedals, 

 couplers, and other features became necessary as a part of the 

 major development, viz., the modern great organ as it stands. Of 

 electricity and pneumatics nothing more need be said save that 

 these agencies have been found invaluable in operating massive 

 instruments. 



A description of the Tabernacle organ in Brooklyn will show 

 the mechanical and scientific points of interest contained in a 

 modern instrument of that class: The great-organ key-board 

 (A) is capable of controlling all the others — namely, swell (B), 

 choir (C), and solo organ (D). In effect, the great-organ key- 

 board through the tracker (A) and squares (A) opens the ports 

 of the pneumatic chest (E), the interior of one of which is shown. 

 This is filled with compressed air of a power and quantity capa- 

 ble of raising a column of water seven inches. When the key 

 is pressed, or operated, it opens the vent-valve (G) and closes 

 the supply-valve (H). The compressed air from the chest presses 

 on the top of the small bellows (I), one of which is furnished to 

 each note, and the wind, consequently escaping through the vent- 

 valve, pulls the wire of lever (J) and tracker (J). This passes 

 up and pulls open the big valve in the great-organ wind chest, 

 and affects all the other organs also, when coupled on to the 

 tracker indicated. 



To explain the action of the choir key-board (C) : On being 

 pressed, the key (C) opens the train of trackers and connections 

 (K) ; the vent-valve (L) in that chest is opened, which closes the 

 supply-valve (N), thereby allowing wind to escape from the small 



