1869.] 



on the Mechanical Pro])erties of Steel. 



27 



CoMPABisoN of Steel — continued. 

 Table III. — Compeessive Strain on specimens f in. diameter and 1 in. in length. 



are considerations of great importance ; and in every case where 

 steel can be depended upon, it is entitled, on tlie score of economy 

 and lightness, to the judgment and practical knowledge of the 

 architect and engineer. 



In Table III., on compression, each of the specimens were 

 reduced, when cut from the bars previously experimented upon, to 

 small columns of | inch diameter and 1 inch in height. They 

 were each loaded with weights equal to 100 tons per square inch, 

 without undergoing any sensible appearance of fracture. On con- 

 sulting the Table it will be .found that with the above weight of 

 100 tons per square inch they were compressed, on the average, 

 to two-thirds their original length ; and from these facts we were 

 enabled to find the value of u, recorded in the last column, as 

 the value of work done by the load which produced the change of 

 form in each of the specimens submitted to pressure. This, it will 

 be observed, was the true test of the powers of resistance of the 

 respective specimens to a compressive strain, and the conditions 

 under which materials of similar properties may be safely applied in 

 constructive art. 



On comparing the mean tensile resistance to rupture at 47*7 

 tons per square inch, it will be seen that the resistance to com- 



