Farms and Villages. 
59 
lower valve ; the delivery-pipe issues just below the air-vessel 
over the upper valve. When the ram is in action, the piston, 
which has replaced the valve D, works up and down like that of 
a pump of short stroke ; each blow sends it up, and each recoil 
sucks it down. In the down-stroke it draws up the pure water 
Fig. 9. — Elevation {sails open) of the Halladay Windmill. 
from the supply, and in the up-stroke discharges it into the 
rising main. Rams so arranged will not suck up water more 
than a very few feet ; it is therefore desirable to arrange for the 
pure water being as near the level of the ram as possible. The 
height to which they will suck depends upon the strength of 
the spring which forces down the piston. 
