200 MACHIXERY IX COXNECTIOX WITH -WATER. 



of fourteen inches ;'' one pound will fill it twenty-eight 

 Fig. 226. inches ; two pounds, fifty-six inches ; 



iibs. 56 in. ten pounds, twenty-three feet ; twenty 

 pounds, forty-six feet, and so on. 

 Now, as the side pressure is the same 

 as the pressure downward for the 

 -i>iibs,.i2in. same head of water, the same column 

 will, of course, exert an equal pressure 

 on a square inch of the side of the 

 tube. Or, if the tube be bent, as 

 lib 28 iu. shown in the annexed figure (fig. 



226), the pressure upward on the end 

 of the tube, at a, will be the same for 

 the various heights. 

 1/2 lb. 14 in. Now, as the pressure of a column 



fifty feet high is about twenty-two 

 pounds on a square inch, the pressure 

 on the four sides is equal to eighty- 

 eight pounds for one inch in length. 

 Hence the reason that considerable 

 strength is required in tubes which 



have much head of water, to prevent their being torn 



open by its force. 



DETERMINING THE STRENGTH OF PIPES. 



The question may now arise, and it is a very important 

 one. How thick must be a lead tube of this size to prevent 

 danger of bursting with a head of fifty feet, or of any 

 other heiffht? To answer it, let us turn to the table of 

 Ihe Strength of Materials in a former part of this work, 

 where we find that a bar of cast lead one-fourth of an 

 inch square will bear a weight of fifty-five pounds. If the 



* This is nearly correct, for a cubic foot (or 1,738 cubic inches) of 

 water weij^hs 63 lbs. Consequently, one pound will be 37.9 cubic inch- 

 es, and will fill the tube nearly 38 inches high. 



