OF IRON BEAMS. 507 



ac zz length of wedge = 4.2 inches. 



bd = depth of wedge =1.7 „ 

 25144 lbs. = 11 tons 4i cwt. = breaking weight. 

 Hence strength per square inch of section = 

 «i?ii= 3492 lbs. 



To compare this with the results from the 

 common beam, we will take the mean between 

 those in experiments 4 and 34, they being both 

 supposed to be from the same sort of iron, 

 and the only ones that were cast on their 

 sides. Experiment 4, gave 2584 lbs., and 

 experiment 31, 3009 lbs. per inch : mean 

 = 2796. 



.-. 3492 - 2796 = 696 = excess. 

 Pence saving in metal, from section, = 



696 , - - - 



5^ linearly. . , 



If we compare this beam, by weight, with 

 the mean weights derived from experiments 

 4 and 34; since in the former, 40| lbs. bore 

 8270, and in the Isitter, 36i bore 8792 ; taking 

 the sums, 77 lbs. bore 17062 lbs. 



.% 77 : 81 lbs. (the weight of this beam) 

 :: 17062 : 17948 lbs. = weight it should have 

 borne; but it did bear 25144, /. 25144 - 17948 

 =;: 7196 = excess. 



Hence saving in metal from section and ends 



- 26141 - -^^^^ 



3 s 2 



