BOOK VI. 



A— Sills. B— Pointed stakes. C — Cross-beams. D — Upright Planks. 



E — Hollows. F — Winds. G — Covering disc. H — Shafts. I — Machine 



without a covering. 



The second machine of this genus turns the blowing wind into a shaft 

 through a long box-shaped conduit, which is made of as many lengths of 

 planks, joined together, as the depth of the shaft requires ; the joints are 

 smeared with fat, glutinous clay moistened with water. The mouth of this con- 

 duit either projects out of the shaft to a height of three or four feet, or it does 

 not project ; if it projects, it is shaped Uke a rectangular funnel, broader and 

 wider at the top than the conduit itself, that it may the more easily gather 

 the wind ; if it does not project, it is not broader than the conduit, but 

 planks are fixed to it away from the direction in which the wind is blowing, 

 which catch the wind and force it into the conduit. 



The third of this genus of machine is made of a pipe or pipes and 

 a barrel. Above the uppermost pipe there is erected a wooden barrel, four 



