178 



BOOK VI. 



A — Erect timber. B — Axle. C — Sweep which turns about the axle. D — Piston 

 ROD. E — Cross-bar. F — Ring with which two pipes are generally joined. 



an iron axle, so fastened in the holes in the fork that it remains fixed, and 

 the sweep turns on this axle. In one end of the sweep the upper end of a 

 piston-rod is fastened with an iron key ; at the other end a cross-bar is also 

 fixed, to the extreme ends of which are handles to enable it to be held more 

 firmly in the hands. And so when the workman pulls the cross-bar upward, 

 he forces the piston into the pipe ; when he pushes it down again he draws 

 the piston out of the pipe ; and thus the piston carries up the water which 

 has been drawn in at the openings of the disc, and the water flows away through 

 the spout into the drains. This pump, Uke the next one, is identical with 

 the first in all that relates to the piston, disc, trunk, box, and valve. 



The third pump is not unlike the one just described, but in place of 

 one upright, posts are erected with holes at the top, and in these holes the 

 ends of an axle revolve. To the middle of this axle are fixed two wooden 

 bars, to the end of one of which is fixed the piston, and to the end of the 

 other a heavy piece of wood, but short, so that it can pass between the two 

 posts and may move backward and forward. When the workman pushes 

 this piece of wood, the piston is drawn out of the pipe ; when it returns by its 



