OF IRON BEAMS. 619 



the separation of a wedge ; and consequently 

 by the rupture of a part, whose strength was 

 not so well proportioned as that of the bottom 

 rib, which must have been torn asunder first, 

 if the beams had broke by tension. 



The superior thickness of the vertical part 

 near the bottom rib prevented, as was intended, 

 the fracture taking place as in experiment 19, 

 by the breaking out of a wedge near the neutral 

 line ; but it was only that, as in experiment 28, 

 a wedge of a less size, and of the same form, 

 might break out higher up, where the vertical 

 part was thinner. It seems then probable, from 

 these experiments, that no advantage would 

 accrue from making the vertical part of 

 unequal thickness. 



Comparing the weights of the beams in expe- 

 riments 32 and 33, with the loads they bore, 

 we see that a great increase of strength may 

 be obtained through a small additional w^eight 

 of metal, when the depth can be increased.* 



♦ It is not always advisable to increase the depth of a 

 beann, when we have the means of doing it ; as it would lessen 

 iu flexibility, and render it liable to be broke by percussion, 

 through wcij^'hts fallinjr upon it. Sonrje experiments on the 

 resistance of beams, to impulsive forces, which I commenced on 

 a large scale some time ago, through the liberal views of 

 Messrs. Fairbairn and Lillie, may probably in an extended 

 form be offered, at some future period, to the Public. 



