CURRENTS COUNTERACT VIBRATIONS. 



Then the continuous vibrations of the air 

 against the one side of the piston predominate, 

 and, being relieved from the action of an equal 

 force on the other side, produce a resultant move- 

 ment of the piston. Instead of the complex ap- 

 paratus of an air-pump for producing a vacuum, 

 a simple plan is employed in the mechanics of 

 Nature, by merely changing the vibrations im- 

 pinging directly against the surface of a body 

 to another direction parallel with the surface. 



Jet-pumps constructed on this peculiar principle 

 are now used instead of air-pumps, to produce a 

 vacuum for raising water by atmospheric pressure. 

 A swift current of air, of steam, or of water, in 

 a jet from the pipe A, will convert the atmospheric 

 vibrations into a rectilinear current through the 

 pipe c ; as represented in Fig. 16. 



The atmospheric vibrations in the pipe B, im- 

 mersed in water, are changed from a vertical di- 

 rection against the 

 surface of the water 

 at the lower end of 

 the pipe B, to a hor- 

 izontal direction in 

 the pipe c, parallel 

 with the surface of 

 the water. By thus 

 relieving the water 

 in the lower end of 

 the pipe B from ver- fi f . 16. 



