TRANSACTIONS OF THE SECTIONS. 207 



Trade would make suitable provision in its regulations for the employment of such 

 material. 



The difficulty lies in the want of something whereby the quality of the metal 

 may be known and relied upon with confidence by others besides those who made 

 the article. 



In gold and silver this is accomplished by the stamp put upon them, in guns and 

 small arms we have the proof-mark, but iu iron and steel we liave nothing whereby 

 the one quality of metal can be distinguished from another ; and mitil some suffi- 

 cient means be devised for this purpose, it is difficult to see how we are to escape 

 from the position in which we are now placed — namely, that while we possess a 

 material by which we can increase considerably the spans and diminish the weight 

 and cost of engineering works, we are restricted to malce designs and construct our 

 works by a rule made for wi'ought iron, and adapted to the lowest quality of that 

 material. 



As the rule made by the Board of Trade in respect of ^\TOught-iron railway struc- 

 tures may not be generally known, I here give it : — 



" In a wrought-iron bridge, the greatest load which can be brought upon it, added 

 " to the weight of the superstructure, should not produce a greater strain on any 

 " ptart of the material than five tons per inch." 



It will be observed that this o tons per inch is the governing element, irrespec- 

 tive entirely of the quality of metal used ; and it is obvious that a rule so framed 

 must act as a discouragement to any endeavour to improve the quality of metal, 

 while it tends to induce the employment of the cheapest and most inferior descrip- 

 tions which can be made under the name of wrouglit iron. 



In endeavouring to seek an amendment of the rules, which will permit of the 

 employment of steel or other metal of higher strength than 5 tons to the inch, I 

 feel bound to say that I do not consider that the Board of Trade is alone responsi- 

 ble for the position in which the question now stands ; and, as regards the Govern- 

 ment Inspecting Officers, I can only say that in the numerous transactions I have 

 had with them, and although dift'erences of opinion have occasionally arisen, yet, 

 considering the responsibility which rests upon them, I have found them anxious 

 to aftbrd all reasonable facilities so far as their instructions permitted. 



The first step to be taken is to put our testing on a systematic and satisfactory basis. 



The second is to establish some means whereby metal which has been tested 

 can have its quality indicated upon it iu such manner that it can be practically 

 relied upon. 



The experiments before referred to establish, sufficiently for all practical pur- 

 poses, that the relation or proportion between the resistances to tension, compres- 

 sion, torsion, and transverse strain is about the same iu steel as in wrought iron. 



The testing required is therefore reduced to that necessary for ascertaining two 

 properties only, namely the strength and the toughness or ductility. 



The strength may be readily ascertained, and no difficulty arises on that head. 



The whole question turns upon the test for ductilitj', or the resistance to fracture 

 by blows or sudden strain ; and it must be admitted that the tests employed for 

 this purpose are not framed on any regular or satisfactory basis. 



I may mention as an example the test of rails by a falling weight. 



In the first place, as usually applied, it is made a destructive test, the weight and 

 fall being such as to bend and render the rail unfit for use, however good its quality 

 may be. 



Secondly, being a destructive test, it is applied only to 1 or 2 per cent, of tha 

 quantity ; and if this amount bear the test, the remainder are assumed to be like 

 them. I have recently had occasion to know, in a case which came before me re- 

 specting iron rails, that this assumption may be entirely fallacious. 



Again, we find 10 to 18 cwt. fiiUing 5 feet used for iron rails, while 1 ton falling 

 20 feet and sometimes 30 feet is specified for steel, and yet both descriptions 

 of rail are called upon to perform the same work when laid down in the road. 



I believe the falling weight, or, in other words, the test by impact, to be a good 

 and searching test for detecting brittleness ; and it has the advantage of being 

 cheap, quick, and easy of application, but it is questionable if it is applied iu the 

 best manner. 



