308 



Theory of the Pneumatic Paradox. 



one line in diameter, and situated two and six inches respectively 

 below the ajutage. To the top were soldered two leaden tubes, 

 the larger six feet high and three quarters of an inch in diame- 

 ier, and surmounted by a funnel; and the smaller somewhat 

 shorter, and terminating above in a glass tube. A shelf of tin- 

 red sheet iron five or six inches wide, was soldered to the oppo- 

 site sides of the vessel, so as to cross it two inches from the top, 

 under the end of the larger tube. The accompany- pig_ 5_ 

 ing figure exhibits the form, though not the relative 

 proportions, of the several parts of the apparatus. 

 The whole was supported by frame-work, not seen 

 in the figure. The end of the descending tube, and 

 also the lateral holes, being stopped, and the vessel 

 and tubes being kept full of water to the brim of the 

 funnel, which was somewhat more than seven feet 

 above the bottom of the vessel, on removing the oiled 

 silk from either lateral hole, a horizontal jet issued, 

 which reached the distance of seven and a half feet 

 before falling to the brick pavement, situated two and 

 a half feet below the bottom of the vessel. On un- 

 stopping the lower end of the triblet tube, the water 

 immediately sunk nine inches in the small glass tube below its 

 level in the large tube, showing a diminution of the effective head 

 to that amount. Meanwhile the jet continued to issue from the 

 lateral holes, but it assumed, owing to the joint action of onward 

 and lateral forces, instead of a horizontal direction as before, an 

 oblique downward one, which would of course prevent its attain- 

 ing the random due to the actual pressure against the surface of 

 the tube, and it reached the pavement at the horizontal distance 

 of a little more than three feet. The distance became less by 

 diminishing the head of water. Jets of nearly equal force issued 

 from the lateral holes when a similar descending tube without an 

 ajutage was used. 



This result completes the proof of the proposition I have been 

 endeavoring to establish, that water, flowing through a cylindrical 

 tube, whether in a horizontal, inclined, or — if short — in a verti- 

 cal position, exerts, contrary to the principle laid down by Bossut 

 and others, a lateral pressure, varying with its incumbent head 

 and independent of its weight, against the interior surface of the 



