LIFTING '-P UMP. 



175 



FIG. in. 



moving sidewise. The edges being greased and placed together, the 

 air is exhausted from the hollow globe through a tube provided 

 with a stop-cock and screw. When the air has been 

 pumped out, close the stop -cock, remove the hemi- 

 spheres from the pump, and screw a convenient 

 handle upon the lower hemisphere, the upper one 

 being provided with a permanent handle. It will 

 be found that a considerable force is necessary to 

 pull the hemispheres asunder. This force is equal 

 to the atmospheric pressure upon the circular area 

 inclosed by the edges of the hemispheres. If this 

 area be ten square inches it will require a pull of 

 150 pounds to separate the hemispheres. 



(13.) Partly fill two bottles with water. Connect 

 them by a bent tube which fits 

 closely into the mouth of one and 

 loosely into the mouth of the other. Place the bot- 

 tles under the receiver and exhaust the air. Water 

 will be driven from the closely stoppered bottle 

 into the other. Readmit air to the receiver and the 

 water thus driven over will be forced back. 



294. The Lifting FlG II2 

 Pump. The lifting-, 

 pump consists of a cylinder or bar- 

 rel, piston, two valves, and a suc- 

 tion pipe, the lower end of which 

 %Sj dips below the surface of the liquid 

 to be raised. The arrangement is 

 essentially the same as in the air- 

 pump. As the piston is worked, 

 the air below it is gradually re- 

 moved. The downward pressure on 

 the liquid in the pipe being thus 

 removed, the transmitted pres- 

 sure of the atmosphere, exerted; 

 upon the surface of the liquid, 

 pushes the liquid up through 



FIG. 



