Theory of the Pneumatic Paradox. 303 



The following is the experiment of Venturi, cited in proof of it. 



Fig. 2. 



To an orifice near the bottom of a reservoir, in which water 

 was maintained at the constant height of 31.5 inches above the 

 centre of the orifice, he adapted the tube KLV, one inch and a 

 half in diameter, and four inches and three quarters in length. 

 Into the tube KLV was inserted the glass tube Q,RS, at the dis- 

 tance of two thirds of an inch from the orifice KL. The lower 

 end was plunged in colored water, contained in the vessel T. 

 The efflux of water through the tube being permitted to take 

 place, four cubic feet flowed out in thirty one seconds, and the 

 colored water in T rose in the tube to S, twenty four inches 

 above the surface of the water in T. The branch RT was short- 

 ened so that RT was only six inches longer than R(i, and the 

 colored liquid in T rose through RS, and mixed with the water 

 that flowed from the reservoir through the tube KLY, and in a 

 short time the water in the vessel T was emptied. The same 

 effect takes place when the tube KLY is directed upwards or 

 downwards. 



The true explanation of these and kindred experiments of 

 Yenturi, is found in a fact, apparently overlooked by those who 

 have adduced them as proofs of the general principle, that liquids 

 flowing through a horizontal cylindrical tube, exert no pressure 

 against its interior surface. When water flows through a circular 

 orifice in a thin plate, the jet, in consequence of " the interference 

 of the particles of the fluid coming from the parts on each side of 



