484 THE STRENGTH 



Form of fracture nearly as bnr in figure; 

 bn = 1.8 inches. 



Hence strength per square inch of cross 

 section =^= 3883 lbs. 



. 6.41 



Comparing this with the result from the 

 common beam in experiment 22, which bore 

 2885 lbs. per inch, 3883-2885 = 998 = excess. 



Hence gain in strength = ^ = .345, in 

 terms of what the common beam bore : or 

 saving in metal, from section, =: ^ = .257, or 

 upwards of }. 



If the comparison be made by their weights, 

 the saving in metal will be only .23, which is 

 less than it would have been, had the ends of 

 the beam been formed as in the preceding ones 

 from experiment 13 to this: the bottom rib of 

 this being all of a breadth and thickness and 

 5 feet long ; though the distance of the supports 

 was but 4 feet 6 inches. This remark applies, 

 though in a less degree, to the beams in expts. 

 11 and 12, and those immediately preceeding 

 them I those beams like this having their vertical 



