OF IRON BEAMS. 477 



together, and supposed to have been from the 

 same iron, but the results were so anomalous 

 that nothing could be learned as to the relative 

 strength; there was, however, one fact proved 

 by them and that a very important one ; every 

 beam had broke by tension, or through the 

 weakness of the bottom rib, which though so 

 large had always been torn asunder, while the 

 top part had remained unchanged. It, having 

 been prevented from twisting by the small rib 

 there, shewed no signs of being over compressed. 



44. In the following four experiments, and indeed 

 in all the following ones, a good deal of attention 

 was paid to the iron, it was the same as that 

 used in the commencement of this series, and 

 of which a description has been given : it is a 

 strong iron and was considered by Mr. LHlie 

 as best adapted for beams. 



XIX. EXPERIMENT. 



The last beam having still broke by tension, 

 the bottom rib was again increased, by making 

 it a small portion thicker, but without altering 

 the depth of the beam. 



Distance of supports, 4ft. Gins, and depth of beam, 

 5| inches, as before. 



