178 SIPHON. 



C is lower than mn, the surface of the liquid ; or 

 it may be first placed in position, 

 and the air removed by suction 

 at the lower end ; whereupon, by 

 the pressure of the atmosphere, 

 the fluid will be forced up the 

 shorter arm and fill the tube. In 

 either case a constant stream of 

 the liquid will flow from the upper 

 P IG> TI 6 vessel until the surface line mn is 



brought as low as the opening in 



the shorter arm, or, if the liquid be received in another 

 vessel, until the level is the same in the two vessels. 



299. Explanation of the Siphon. This action 

 of the siphon may be thus explained: For convenience, 

 suppose that the sectional area of the tube is one inch, 

 that the downward pressure of the water in the arm AB 

 is one pound, and that the downward pressure of the water 

 in the arm BC is three pounds. The upward pressure in 

 the tube at A will equal the atmospheric pressure on each 

 inch of the surface mn outside the tube minus the down- 

 ward pressure of one pound, i. e., (15 1 =) 14 pounds. 

 On the other side, there is at C the upward atmospheric 

 pressure of 15 pounds, from which must be taken the 

 downward pressure of the water in BC, leaving a resultant 

 upward pressure of 12 pounds at C. The upward pressure 

 at A being two pounds greater than that at C, determines 

 the flow of the water ABC. The greater the difference 

 between la and be, the greater the velocity of the stream. 



300. Limitations. If the downward pressure at A 

 be equal to the atmospheric pressure, the liquid will not 



