?464 THE STRENGTH 



j Weight of beam = 40i lbs. 



Breaking weight = 8823 lbs. 

 It broke H inches from the middle. The form 

 of fracture was nearly as in experiment 4; 

 here bn = 2.25 and tr = .8 



Hence strength per inch of section = -g-jj- = 

 2792 lbs. 



In the following experiments, the bottom rib 

 is considerably increased, agreeably to the 

 remarks made on experiment 9, but for fear 

 lest the top rib should be overpowered, and 

 by its compression the point of support thrown 

 lower down the beam, and consequently the 

 beam weakened, the top rib was a little 

 strengthened likewise. 



The bottom rib will continue to be increased 

 by small degrees, till such time as the beam 

 breaks by compression, or by the separation of 

 a wedge ; at which point, perhaps, we shall 

 have arrived at nearly the strongest form of 

 section, for the same depth of beam and quantity 

 of section. 



XI. EXPERIMENT. 



Beam from model of experiment 9, only its' 

 top and bottom ribs altered as above, 

 f,,^., Ratio of ribs 1 to 4 nearly. 



Distance between supports and depth as before. * 



