BOOK VI. 



203 



the world it blows, drives the wing straight toward the opposite direction, in 

 which way the barrel turns the blow-hole towards the wind itself ; the 

 blow-hole receives the wind, and it is guided down into the shaft by means 

 of the conduit or pipes. 



A— Wooden barrels. B — Hoops. C — Blow-holes. D — Pipe. 



E — Table. F — Axle. G — Opening in the bottom of the barrel. 



H— Wing. 



The second genus of blowing machine is made with fans, and is Ukewise 

 varied and of many forms, for the fans are either fitted to a windlass barrel 

 or to an axle. If to an axle, they are either contained in a hollow drum, 

 which is made of two wheels and a number of boards joining them together, 

 or else in a box-shaped casing. The drum is stationary and closed on the 

 sides, except for round holes of such size that the axle may turn in them ; 

 it has two square blow-holes, of which the upper one receives the air, while 

 the lower one empties into the conduit through which the air is led down the 

 shaft. The ends of the axle, which project on each side of the drum, are 

 supported by forked posts or hollowed beams plated with thick iron ; one 

 end of the axle has a crank, while in the other end are fixed four rods with 

 thick heavy ends, so that they weight the aixle, and when turned, make it 



