OF IRON BEAMS. 5Sl 



ing with 23, it is evident that, with a given 

 top and bottom rib and thickness of vertical 

 part, we may often beneficially increase the 

 depth of a beam, and that to a considerable 

 •extent; but doubtless, though we have had 

 no experiments suitable to shew it, a less thick- 

 ness of vertical part would have been requured, 

 if the depth of the beam were reduced, its length 

 remaining the same. This matter has been 

 touched on in article 33, (see also Robison's 

 Mechanical Philosophy, vol. 1, article 390), 

 and the experiments will throw additional light 

 upon it; but its further consideration must be 

 deferred to some future opportunity. 



These experiments shew clearly too, that, in 

 some of our earliest experiments, the weakness 

 of the beams, considering the quantity of section, 

 rose principally from the vertical part being 

 too thick. 



Before concluding these remarks, I may further 

 mention, that in all cases where the beam has 

 broke by the separation of a wedge, as in the 

 preceding experiments, its vertical part should 

 be rendered a little stronger, so as just to 

 cause it to break by tension; to which case 

 only, the followmg rules for the strength will 

 properly apply. 



3 u 



