BOOK VI.

203

the world it blows, drives the wing straight toward the opposite direction, inwhich way the barrel turns the blow-hole towards the wind itself; theblow-hole receives the wind, and it is guided down into the shaft by meansof 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.

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The second genus of blowing machine is made with fans, and is likewisevaried and of many forms, for the fans are either fitted to a windlass barrelor 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 thesides, 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, whilethe lower one empties into the conduit through which the air is led down theshaft. The ends of the axle, which project on each side of the drum, aresupported by forked posts or hollowed beams plated with thick iron ; oneend of the axle has a crank, while in the other end are fixed four rods withthick heavy ends, so that they weight the axle, and when turned, make it