428 
” them, in guns and small arms we have the proof-mark, but in 
iron and steel we have nothing whereby the one quality of metal 
can be distinguished from another; and until some sufficient 
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— 
pamely, that while we possess a material by which we can in- 
crease considerably the spans and diminish the weight and cost 
of engineering works, we are restricted to make designs and con- 
struct our works by a rule made for wrought iron, and adapted 
to the lowest quality of that material. 
As the rule made by the Board of Trade in respect of wrought- 
iron railway structures 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 part of the material 
than 5 tons per inch.” ; 
It will be observed that this 5 tons per inch is the governing 
element, irrespective 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 
descriptions which can be made under the name of wrought- 
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 responsible for the 
position in which the question now stands; and as regards the 
Government Inspecting Officers, I can only say that in the 
numerous transactions I have had with them, and although 
differences of opinion have occasionally arisen, yet, considering 
the responsibility which rests upon them, I have found them 
anxious to afford all reasonable facilities so far as their instruc- 
tions permitted. : : 
The first step to be taken is to put our testing on a systematic 
and satisfactory basis. 3 
The second is to establish some means whereby metal which 
has been tested can have its quality indicated upon it in such 
manner that it can be practically relied upon. 334 
The experiments before referred to establish, sufficiently for 
all practical purposes, that the relation or proportion between 
the resistances to tension, compression, torsion, and transverse 
strain, is about the same in steel as in wrought-iron. 
The testing required is therefore reduced to that necessary for 
ascertaining two properties, namely the strength and the toughness 
or ductility. ; ae 
The strength may be readily ascertained, and no difficulty 
arises on that head. = 
The whole question turns upon the test for ductility, 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. a 
Without, however, attempting to say what description of test 
may be found the best for ascertaining the property of ductility, 
it may be observed that what is required for this test is a definite 
basis to act upon, and that the samples should be so made as to 
render the test cheap, expeditious, and easy of application. 
The next requirement is that when a piece of metal has been 
tested, and its qualities of strength and toughness ascertained, 
there should be some means of denoting its quality in an 
authentic manner. 
To a certain extent this is already done in iron by the mark of 
the maker ; but something more than this is necessary to fulfil 
the required conditions in steel. l 
What is termed steel, is iron with a small proportion of carbon 
init. These two ingredients are necessary to constitute steel ; 
and there may or may not be present in very small quantities 
graphite, silicon, manganese, sulphur, and phosphorus. : 
In connection#with the experiments made by the Committee, 
fourteen of the samples were tested by Mr. E. Richards, of the 
Barrow Steel Works, five of which were kindly repeated by 
Dr. Odling. : ‘ 
Although there are some discrepancies in the results which we 
cannot account for, yet some of the characteristics are brought out 
clearly. 
‘Tt Hee that manganese may be present to the extent of four- 
tenths per cent. without injury either to the strength or ductility, 
but sulphur and phosphorus, except in extremely small quanti- 
ties, are fatal to ductility, 
NATURE 
| Sez. 18, 1873 
In the samples tried bythe Committee and Mr, Kirkaldy, the 
quantity of carbon varied from 4 per cent. to nearly r per cent. ; 
yet with this small variation in the carbon the strength ranged 
from thirty-three tons to nearly fifty-three tons per in. : and the 
ductility, represented by the ratio which the fractured area bore 
to the original section of the bar, varied from five-tenths in the 
tough qualities, until in the harder samples there was no diminu- 
tion perceptible. - 
’ All these materials are called steel, and have the same external 
appearance ; but possessing, as they do, such a range of strength 
and such a variation in ductility, it becomes absolutely essential 
that there should be some classification or means of knowing the 
respective qualities among them. 
The want of such classification casts an air of uncertainty over 
the whole question of steel, and impedes its application. To 
this want of knowledge is to be ascribed the circumstance that 
many professional men regard the material as altogether unre- 
liable ; while large consumers of steel, in consequence of the un- 
certainty of the quality they buy in the market, seek to establish 
works on their own premises and make their own steel. 
I ought, I know, to apologise for detaining you so long on this 
one question of steel, but I consider that the difficulties under 
which it is placed are affecting interests of considerable impor- 
tance. 
Not only is a large and useful field for the employment of 
steel practically closed, but the progress of improvement in 
engineering structures is impeded both in this country and in 
other parts of the world where English engineers are engaged. 
For in consequence of the impediments to its employment in 
England, very few English engineers turn their attention to the 
use of steel. They are accustomed to make their designs for 
iron, and when engaged in works abroad where the Board of 
Trade rules do not apply, they continue for the most part to 
send out the, old-fashioned ponderous girders of common iron, 
in cases where the freight and difficulties of carriage make it 
extremely desirable that structures of less weight and more easy 
transport should be employed. 
In conclusion, and while thanking you for the patience with 
which you have heard me on this subject, I would observe that 
we possess in steel a material which has been proved, by the 
numerous uses to which it is applied, to be of great capability 
and value: we know that it is used for structural purposes in 
other countries, as, for example, in the Illinois and St. Louis 
Bridge in America, a bridge of three arches, each 500 ft. span ; 
yet in this country, where ‘‘ modern steel” has originated and 
has been brought to its present state of perfection, we are ob- 
structed by some deficiency in our arrangements, and by the 
absence of suitable regulations by the Board of Trade, from 
making use of it in engineering works, 
And I have considered it right to draw your attention to the 
position in which this question stands, well knowing that I could 
not addressany body of gentlemen more capable of improving 
and systematising our methods of testing, or better able to devise 
effectual means for removing the impediments to the use of steel, 
than are to be found in the scientific and practical mea who form 
the Mechanical Section of the British Association. 
CONTENTS 
Pace 
Screntiric Wortutes, I. FarApay (With Steel Engravilg). « . 307 
LETTERS TO THE EpITOR:— 
Tyndall and Tait.—Prof. Joun Tynpaut, I-R.S. « oe « « 399 
NorEs FROM THE Challenger,VII. By Prof. Wyvitte THomson,F.R.S. 
(With Mlustrations) <6 ies +)\0 e's «in ke) ee 
Tue INTERNATIONAL .MeTric Commission AT Paris. By H, W, 
CHISHOLM o's 5's syne 2 0s ss » 6) © les 
NoOrks 20% so 6) 3 wiles lee 86 ee 0) fou 
SocreTigs AND ACADEMIES 6 9. « « » « © « » "6 6 same 
Tue Britisu AssociaTION MEETING AT BRADFORD. . . «© + « = 
Opening Address by the President, Prof. Wirttamson, F.R.S. . 
Section B.—Address by the President, Prof. Russert, F.R.S.  . 
Section C. Py) 5 or J. Puituirs, F.R.S 
Section D, Ft 3 = Pror. ALLMAN « A 
Section G, A ” ” W. H. Bartow, F.R.S. . 
