i\Ir. Barlow on an element of Strength in Beams. 



51 



and lower bars of the same beam were in every case of the same 

 form and dimensions ; but the depth of metal and the distance to 

 which the bars were separated vertically, was varied in the several 

 forms of girder experimented upon. By these means the bar form- 

 ing the lower side of each girder was torn asunder under different 

 degrees of flexure. The different forms of girder experimented 

 upon were of equal length, and were compared with solid beams and 

 with bars of the same metal broken by direct tensile strain. 



From the mean oi four experiments on each form of girder, the 

 value of the total resistance at the outer fibre is ascertained, and 

 exhibits the following results : — 



1. In girders having the same depth of metal, namely about 2 

 inches, but the total depth of the girder, and consequently the 

 deflections different — 



2, In girders having the same total depth (namely 4 inches), and 

 consequently nearly tiie same deflection, but dift'ering in the depth 

 of metal — 



From these experiments, the particulars of which are fully de- 

 tailed, the following facts are elicited : — 



1. That in all cases the total resistance at the outer fibre, at the 

 time of rupture, is greater than the tensile strength, 



2. That in girders having the same depth of metal, it increases 

 when the deflection increases ; and 



3. That in girders having the same total depth, and the same de- 

 flection, the resistance is greater when the depth of metal in the 

 beam is greater. 



And it follows tliat tiiere is an element of strength depending on 

 the depth of metal in connexion with the deflection ; or in other 

 words, de])endent on the deyree oi Jiexttre to whicli the metal form- 

 ing the beam is subjected. 



E2 



