EXPERIMENTS UPON WROUGHT-IRON GIRDERS. 47 



Table I. — Experiment on Wrought-iron Beam with a changing load 

 equivalent to one-fourth of the breaking weight. 



As the beam had now undergone above half a million changes of load, 

 that is, it had worked continuously for two months, night and day, at the 

 rate of about eight changes per minute, and as it had undergone no visible 

 alteration, the load was increased from one-fourth to two-sevenths of the 

 statical breaking weight, and the experiment proceeded with till the number 



of changes of load reached a million. 



Table II. — Experiment on the same Beam with a load equivalent to two- 

 sevenths of the breaking weight, or nearly 3y tons. 



