206 REPORT— 1873. 



tons per inch, show a decrease of ductility somewhat in the same ratio as the 

 strength increases. 



Without going into the numerous achievements of Sir Joseph Whitworth re- 

 sulting from the employment of steel, in connexion with the extreme accuracy of 

 workmanship produced at his works, or doing more than mention the flat-ended 

 steel shot and shell which pass through iron plates when fired obliquely or pene- 

 trate ships' sides below the level of the water, I would call attention to those 

 applications of steel which bear upon its strength and toughness. 



In the first place, there are small arms made entirely of steel, of wonderful range 

 and accuracy, capable of penetrating Si half-inch planks, which is about three times 

 the penetrating power of the Enfield rifle. 



Secondly, tliere are the large guns, also entirely of steel, throwing projectiles from 

 250 lbs. to' 310 lbs. in weight, and burning from 40 to 50 lbs. of powder at a charge, 

 with which a range of nearly 6^ miles is obtained. 



In both these cases the degree of strength and toughness required in the metal is 

 much greater than is necessary for engineering structures. 



It is unnecessary to occupy more time in multiplying examples of the toughness of 

 steel. It is well known to manufacturers, and must also be well known to many 

 others here present, that steel of the strength of 3.3 or 30 tons per inch can be made, 

 and is made in large quantities, at moderate price, possessing aU the toughness and 

 malleability required in engineering structures. 



I Avill proceed, therefore, to the second part of the subject — namely, the want of 

 means of knowing that a given sample of steel is of the quality suited for structural 

 purposes. 



"With most other metals chemical analysis is in itself a complete and sufficient 

 test of quality, but in steel it is not so. The toughness of steel may be altered by 

 sudden cooling; and although the effect of this operation, and generally the effects 

 of tempering, are gTeater when the quantity of carbon is considerable, yet it acts 

 more or less in the mild qiualities of steel ; so that we cannot rely entirely on the 

 aid of the chemist, but must fall back on mechanical tests. And in point of fact, 

 seeing that the qualities required are mechanical, it is no more than reasonable that 

 the test should be mechanical ; for this includes not only the test of material but 

 of workmanship. 



Now there are two descriptions of mechanical testing, which may be distin- 

 guished as destructive and non-destructive — the one being beyond and the other 

 within the elastic limit of the material. The destructive test is that usually applied 

 to a part of an article manufactured, as, for example, a piece cut off a boiler-plate 

 and tested by absolute rupture, or by bending or otherwise, whereby the strength 

 and quality of the material in the plate is known. 



The non-destructive test is that usually applied to the finished work, as in the 

 test of a boiler by hydraulic pressure, or the testing of a gim by the proof-charge. 

 The strain in this case is made greater than that which will arise in the daily use 

 of the article, but is not so gi-eatly in excess as to be beyond the elastic limit of the 

 material. 



As regards engineering structures, this second test is easy of application ; but it 

 affords no sufficient criterion that tlie metal possesses that degree of toughness 

 necessary to resist the action of sudden strains. 



It may be said that engineers may ascertain for themselves, by inspection and test- 

 ing at the works, that they are being supplied with the material that they require ; 

 but assuming that the tests and mode of testing were in all respects satisfactory to 

 them, and that the metal supplied was of the right quality, we have still to comply 

 with the conditions prescribed by the Act for the Regulation of Railways, and we 

 must satisfy the Government Inspector. 



It is not to be supposed that he can attend all the required tests at the works ; 

 and the questiou remains, How is the Inspecting Officer of the Board of Trade to 

 be enabled to distinguish the quality of metal in a tinisiied bridge, when he is called 

 upon to give a certificate that it is safe for public traffic ? 



If we could adduce clear and distinct evidence that the metal used for a bridge 

 was of a qualitv which would bear 8 tons to the inch with as much safety aa 

 common iron can bear 5 tons, there can be no reasonable doubt that the Board of 



