OF IRON BEAMS. 497 



Weights. Deflection*. Retorned to. 



11397 68 ... - .16 



12087 ... - .63* .16 



15129 = 6 tons 15 cwt. 9 lbs. 

 It broke by tension very near the middle with 

 this weight, others having been laid on pro- 

 gressively up to it. 



■■V? 



55. This beam being nearly of the same depth 

 with those in the preceding series, we may 

 compare the strength of its iron with that in 

 the last of those experiments. 



Hence strength per inch of section = J|^ = 

 2180 lbs. To find what this quantity would have 

 been, if the beam had been only 4 feet 6 inches 

 long between the props, as in our first 22 

 experiments. 4 feet 6 inches : 7 feet, or 9 : 14:: 

 2180 : 3391 lbs. per inch; which quantity is 

 less than that in experiments 19, 20, and 21 ; 

 the iron is therefore a little weaker. 



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* After the beam had been bent to .63, it had the weight 

 taken off the middle, and 14345 lbs. or 6 tons 8 cwt. gradually 

 laid on it, half way between the middle and the end. It would 

 doubtless have borne considerably more there, but was not 

 tried further, as the intention was to break it by a weight 

 in the middle. 



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