DETERMINING THE PRESSURE ON GIVEN SURFACES. 181 



the water being equally high in both, the pressure on 

 the whole bottom of b will be nine times as great as 

 on the bottom of a ; or any one inch of the bottom of 

 h will receive as great a pressure as the bottom of a. 

 Again, if the vessel c, broad at the top, be narrowed to 

 only an inch in diameter at bottom, the pressure upon 

 that inch will still be the same, most of the weight of 

 its contents resting against the sides, d d. 



If the vessel, A {Fig. 152), be filled with water to a 

 height of fourteen inches, the press- 

 ure will be half a pound on every 

 square inch of the bottom, or upon 

 every square inch of the sides four- 

 teen inches below the surface. If 

 the tube, C, be an inch square, the 

 water wiU be driven into it with a 

 force of half a pound, and will press 

 with that force against the one-inch 

 surface of the stop-cock, C. If the tube, B, be now 

 filled to an equal height, the same force will be exert- 

 ed against the other side. To prove this, let the stop- 

 cock be opened, when the two columns of water will 

 remain at an exact level. 



If enough water be now poured into the tube, B, to 

 fiU it to the top, it will immediately settle down on a 

 level with the water m A, raising the whole surface 

 in the latter. This result has seemed very strange to 

 many, who can not conceive how a small column of 

 water can be made to balance a large one, and it has 

 been therefore termed the Hydrostatic Paradox. But 

 the difficulty entirely vanishes, and ceases to appear a 

 paradox, when we remember that the water in the 



