BOOK VI. 



163 



A— Upright axle. B— Block. C — Roof beam. D— Wheel. E — Toothed-drum. 

 F — Horizontal axle. G— Drum composed of rundles. H — Drawing rope. 

 I — Pole. K — Upright posts. L — Cleats on the wheel. 



wheel made of thick planks joined firmly together, and at its upper end a 

 toothed drum ; this toothed drum turns another drum made of rundles, which 

 is on a horizontal axle. A winding-rope is wound around this latter axle, 

 which turns in iron bearings set in the beams. So that they may not fall, the 

 two workmen grasp with their hands a pole fixed to two upright posts, and 

 then pushing the cleats of the lower wheel backward with their feet, they 

 revolve the machine ; as often as they have drawn up and emptied one 

 bucket full of excavated material, they turn the machine in the opposite 

 direction and draw out another. 



The fourth machine raises burdens once and a half as large again as the 

 two machines first explained. When it is made, sixteen beams are erected 

 each forty feet long, one foot thick and one foot wide, joined at the top with 

 clamps and widely separated at the bottom. The lower ends of all of 

 them are mortised into separate sills laid flat upon the ground ; these sills 

 are five feet long, a foot and a half wide, and a foot thick. Each beam is also 

 connected with its sill by a post, whose upper end is mortised into the beam 



