24 Experimental Researches [Jan., 



be relied upon in tlie selection of the material for the different 

 forms of construction. 



For several years past, attempts have been made to substitute 

 steel for iron, on account of its superior tenacity in the construction 

 of ships, boilers, bridges, &c. ; and there can be no doubt as to the 

 desirability of employing a material of the same weight and of double 

 the strength, provided it can at all times be relied upon. Some 

 difficulties, however, exist, and until they are removed it would not 

 be safe to make the transfer from iron to steel. These difficulties 

 may be summed up in a few words, viz. the want of uniformity in 

 the manufacture, in cases of rolled plates and other articles, which 

 require perfect resemblance in character, and the uncertainty which 

 pervades its production. Time and a close observation of facts in 

 connection with the difterent j)rocesses will, however, surmount these 

 difficulties, and will enable the manufacturer to jiroduce steel in all 

 its varieties with the same certainty as he formerly attained in the 

 manufacture of iron. 



In the selection of the different specimens of steel, I have 

 endeavoured to obtain such information about the ores, fuel, and 

 process of manufacture as the parties supplying the specimens were 

 disposed to furnish. To a series of questions, answers were, in 

 most cases, cheerfully given, the particulars of which will be found 

 in the experimental Tables, published in the Transactions of the 

 British Association for 18G7. 



I have intimated that the specimens have been submitted to 

 transverse, tensile, and compressive strain, and the summaries of 

 results will indicate the uses to which the different specimens may 

 be applied. Table I. gives for each sjtecimen the modulus of elas- 

 ticity, and the modulus of resistance to impact, together with the 

 deflection for unity of pressure ; from these experimental data the 

 engineer and architect may select the steel possessing the actual 

 quality required for any particular structure. This will be found 

 especially requisite in the construction of boilers, ships, bridges, and 

 other structures subjected to severe strains, where safety, strength, 

 and economy should be kept in view. 



In the case of transverse strain some difficulties presented them- 

 selves in the course of the experiments, arising from the ductile 

 nature of some part of the material, and from its tendency to bend 

 or deflect to a considerable depth without fracture. 



But this is always the case witli tough bars, whether of ii'on 

 or steel, and hence the necessity of fixing upon some unit of measure 

 of the deflections, in order to compare the flexibility of the bars 

 with one another, and, from the mean value of this unit of deflection, 

 to obtain a mean value of the modulus of elasticity (E) for the 

 different bars. This unit or measure of flexibihty given in the Table, 

 is the mean value of all the deflections corresponding to unity of 



