264 LETTERS ON NATURAL MAGIC. 



which, by the aid of several wheels, gave a rotatory motion 

 to a steel axis about 2J feet long, having cranks at six 

 equidistant points of its length, but lying in different 

 directions. To each crank was attached a cord, which 

 descended and was fixed by its other end to the upper 

 board of a pair of bellows, 2J feet long and six inches 

 wide. Six pair of bellows arranged along the bottom of 

 the pedestal were then wrought, or made to blow in 

 succession, by turning the steel axis. 



At the upper face of the pedestal, and upon each pair of 

 bellows, is a double pulley, one of whose rims is 3 inches 

 in diameter, and the other 1J. The cord which proceeds 

 from the crank coils round the smallest of these pulleys, 

 and that which is fixed to the upper board of the bellows 

 goes round the larger pulley. By this means the upper 

 board of the bellows is made to rise higher than if the 

 cords went directly from them to the cranks. 



Bound the larger rims of three of these pulleys, viz., 

 those on the right hand, there are coiled three cords, 

 which, by means of several smaller pulleys, terminate in 

 the upper boards of other three pairs of bellows placed on 

 the top of the box. 



The tension of each cord when it begins to raise the 

 board of the bellows to which it is attached, gives motion 

 to a lever placed above it between the axis and the double 

 pulley in the middle and lower region of the box. The 

 other end of this lever keeps open the valve in the lower 

 board of the bellows, and allows the air to enter freely, 

 while the upper board is rising to increase the capacity of 

 the bellows. By this means there is not only power 

 gained, in so far as the air gains easier admission through 

 the valve, but the fluttering noise produced by the action 

 of the air upon the valves is entirely avoided, and the nine 

 pair of bellows are wrought with great ease, and without 

 any concussion or noise. 



