OF IRON BEAMS. 467 



Seeking for the gain, by comparing the 

 weight 67i of this beam, and its breaking 

 M' eight 16730, with the weights 41, and 8942, 

 in experiment 13, we have, as in the last expe- 

 riment, 41 : 8942::67J : 14667. 

 Whence gain = 16730- 14667 =4- nearly: a gain 

 considerably less than that given above, on account 

 of the great weight of the bottom rib ; it being 

 uniform in size through its whole length of 5 feet. 



XIII. EXPERIMENT. 



Beam of the common form, from the same model as the others. 

 Distance between supports as before. 



Dimemions of section in inches (see ^g. to expt. 4.) 



Thickness at A = .29. 



„ B = .425. 



„ „ C = .63 



DE = .565 

 FE = 2.34. 



Area of section = 3.32 inches. 

 Weight of beam = 41 lbs. 



Deflections in inches 

 Weights in Ibt. and parts. 



7598 .4 



8494 .43 



8942 .47, 



with this last it broke after standing a few 

 minutes. It broke H inches from the middle. 



Hence strength per square inch of section 

 = 11 = 2693 lbs. 



% 3 N 2 



