480 THE STRENQTH 



As this is the strongest beam we have tried, 

 if it be compared, by weight, with the result 

 from the very strong beam, of the common 

 form, in experiment 7, the saving in metal 

 will be .29. . ^. [ jq l nh , 



45. Thus we have, by constantly making small 

 additions to the bottom rib, arrived at a point 

 'where resistance to compression could be ' no 

 longer sustained ; but itvvas not till. the bottom 

 rib had considerably moie matter in it thafi 

 double the rest of the beam there, the bottom 

 rib being to tlie rest as 4.4 to 1.83, and to the top 

 rib as 6 to 1.^ — ^Still the top rib was uot .crushed 

 nor shewed any signs of weakness. The frac- 

 ture took place by the vertical part of the 

 beam becoming torn, by the opposite forces of 

 tension and compression round the neutral line 

 (see art. 33), as was the case in the experi- 

 ment ia article 23. 



-:,.■: ;.T ,- — ' ,001^ 



The great strength of this section is an 

 indisputable refutation of that theory, which 

 would make the top and bottom ribs of a cast 

 iron beam equal. 



