186 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK n. 



aperture of the pipes, which then give out the notes corresponding 

 to the notes of the keys of the claviers so depressed. 



In order to ensure steadiness of wind and speech in the pipes it 

 is necessary, in organs of any pretensions, to divide the wind-chest, 

 separating the wind of the lower or bass arid tenor notes which 

 demand a large supply, from the treble notes, which being of much 

 smaller scale require much less wind. Eacli section of the wind- 

 chest is supplied by its own wind-reservoir, and consequently an 

 even and smooth tone is preserved throughout the entire register. 

 Unsteadiness of wind is one of the most serious defects in an organ, 

 the clearness of the articulation of the pipes being thereby destroyed . 



Fit;. 1:55. Wind chest furnished with its pipes. 



Let us now notice each of the parts of the organ that we have 

 just mentioned, in order that the reader may be able to form a clear 

 idea of the working of the various mechanical details of this grand 

 musical apparatus, justly termed the "king of instruments." 



ABC (Fig. 135) is the sound-board. Several series of sonorous 

 pipes, T,T/T," are vertically arranged above the sound-board in 

 parallel rows, each of which forms a stop, such as TT. The lower 

 end of each pipe, termed the "foot," is planted on the sound- 

 board. The wind is brought from the bellows by a wind-trunk 

 to the interior of a sort of box or chest ADD, placed towards 



