464 THE STRENGTH 



beam may be taken as an index of its strength, 

 and we shall use it to compare together the 

 strengths of those beams that are of the same 

 length and depth, which is the case in the 

 first 22 experiments. 



Comparing this with the result from Expt. 4, 

 where the beam bore 2584lbs. per inch, gives 

 2584 - 2368 = 216 = defect. 



.*. Loss in strength = ^^ = .083 or ~ nearly, 

 in parts of what the common beam bore. 



The form of section above is essentially, what 

 Mr. Tredgold has represented to be, that of the 

 strongest beam, while the elasticity is perfect : 

 — our future experiments will render it probable 

 that it is in this respect nearly as defective as it 

 is in its ultimate strength. 



II. EXPERIMENT. 



Beam with areas of section of top and bottom 



rib as 1 to 2. 

 Dist. between supports, 4ft. Gins. Depth of beam, 5iins. 



Detnensions of cross section. 



Area of top rib = 1.74 x .26 =: .45 ins. 

 Area of bottom rib = 1 .78 x -^^ = .98 „ 

 Thickness of the 

 vertical part, 

 Area of cross section = 2.87 inches. 



Weight of casting = 391bs. 



i, ) 



