426 
NATURE 
[ Sept. 18, 1873 
SECTION G.—MECHANICAL SCIENCE 
OpeNING ADDRESS BY THE PRESIDENT, W. H. BARLow, 
C.E., F.R.S. 
In the observations which I have to address to you I shall not 
attempt a general survey of a subject so vast and so varied as 
the manufactures of this country, nor shall I attempt to describe 
the many new and beautiful inventions and mechanical] appliances 
which form a distinguishing feature of the age in which we live ; 
but I shall endeavour to draw your attention to one of the new 
materials, namely modern steel—a material which, though of 
comparatively recent origin, has already become an important 
industry, and whose influence in the future seems destined to vie 
in importance with that resulting from the introduction of iron. 
I have used the term ‘‘ modern steel,” because, although the 
great movement in simplifying and cheapening the process of 
producing steel is necessarily associated with the name of Mr. 
Bessemer, yet we have further important steps taken in a forward 
direction as to the production and treatment of steel by Dr. Sie- 
mens and Sir Joseph Whitworth and others, both in this country 
and abroad. 
It is now seventeen years since Mr. Bessemer read a paper at 
the meeting of the British Association at Cheltenham, which was 
entitled, ‘‘On the Manufacture of Iron and Steel without Fuel.” 
It is satisfactory to know that Mr. Bessemer has often ex- 
pressed his firm conviction that had it not been for the publicity 
given to his invention through the paper which he read before 
the Mechanical Section of the British Association in 1856, and 
the great moral support afforded him by men of science whose 
attention was thereby directed to it, he believes that he would 
not have succeeded in overcoming the strong opposition with 
which his invention was met in other quarters. 
About this time, or perhaps a little later, a material was pro- 
duced called ‘‘ puddled steel,” and about the same time the metal 
known as “homogeneous iron.” 
The movement which had begun’in the production of cheap 
steel was further assisted and developed by the regenerative fur- 
nace of Dr. Siemens, by the introduction of the Siemens-Martin 
process of making steel, and further and most important progress 
is suggested by the recent process introduced by Dr. Siemens in 
making steel direct from the ore. 
According to the returns published by the Jury of the Inter- 
national Exhibition of 1852, the total annual produce of steel in 
Great Britain at that time was 50,000 tons. At the present time 
there are more than 500,000 tons made by the Bessemer process 
alone, added to which Messrs. Siemens’s works at Landore pro- 
duce 200,000 tons, besides further quantities which are made by 
his process at Messrs. Vickers, Messrs, Cammells, the Dowlais, 
and other works. 
I shall not, however, detain you by attempting to trace up the 
history and progress of steel, nor attempt to notice the various 
steps by which this branch of industry has been brought to its 
present important position. My object is to draw attention to 
this material as to its use and application for structural and en- 
gineering purposes, 
The steel produced by the Bessemer process was at a very 
early stage employed in rails and wheel-tires. In both these ap- 
plications the object sought was endurance to resist the effects of 
wear, and toughness to prevent fracture by blows. There does 
not exist at present sufficient information to determine accurately 
the relative values of steel and iron when used for these purposes. 
As used for wheel-tires, steel had to compete with iron of the 
highest quality, but it is nevertheless introduced on most of our 
railways. The iron used in rails was not of such a high quality, 
and the difference in duration shows a very marked advantage in 
the employment of steel, the duration of steel rails being variously 
estimated at from three to six times that of iron. 
Steel is also extensively used for ships’ plates, and by the War 
Department for lining the interior of the heaviest guns ; while 
Sir Joseph Whitworth and Messrs. Krupp make guns entirely 
of steel, though for these purposes the metal is of different 
quality and differently treated, in order to withstand the enor- 
mous concussions to which it is subjected. 
And, further, we have steel used in railway-axles, crank-axles 
for engines, in boilers, in piston-rods, in carriage-springs, and 
for many other purposes. 
But notwithstanding these various employments of steel, there 
has been, and there continues to be, a difficulty in applying it to 
engineering structures in this country. 
The want of knowledge of the physical properties of steel 
having been the subject of remark at a discussion at the Institu- 
tion of Civil Engineers in 1868, a committee, composed of Mr. 
Fowler, Mr. Scott Russell, Captain Galton, Mr. Berkley, and 
myself, undertook to conduct a series of experiments upon this 
subject. : 
The first were made for the Committee by Mr. Kirkaldy with 
his testing-machine in London, and were chiefly directed to as- 
certain the relation which subsists between the resistance of ten- 
sion, compression, torsion, and transverse strain, 
In this series of experiments twenty-nine bars, 15 ft. long, 
were used, each bar being cut into lengths, and turned or planed 
into suitable forms for the respective tests, so that a portion of 
each bar was subjected to each of the above-mentioned tests. 
The tensile resistance varied in the different qualities of steel 
from 28 to 48 tons per inch, and the experiments established 
conclusively that the relation subsisting between the several re- 
sistances of tension, compression, and transverse strain is through- 
out practically the same as in wrought-iron ; that is to say, that 
a bar of steel whose tensile strength is 50 per cent. above that 
of wrought-iron will exhibit about the same relative increase of 
resistance under the other tests. 
They further showed that the limit of elasticity in steel is, like 
that of wrought-iron, rather more than half its ultimate resist- 
ance. The total elongation under tensile strain, and the evi- 
dences of malleability and toughness, will be referred to here- 
after. 
The second series recorded in the book published by the 
Committee gave the results of tempering steel in oil and water. 
They were made by the officers of the gun-factory at the Royal 
Arsenal at Woolwich, and show a remarkable increase of strength 
obtained by this process, This property of steel is now fully 
recognised and made use of in the steel which forms the lining of 
the largest guns. 
The third series of experiments was made by the Committee 
upon bars 14 ft. long, I}in. in diameter, with the skin upon the 
metal as it came from the rolls. 
The object of these experiments was specially directed to as- 
certain the modulus of elasticity. They were made with the test- 
ing-machine at H.M. Dockyard at Woolwich, which machine 
was placed at our disposal by the Admiralty, The bars were 
obtained, with some exceptions, in sets of six from each maker, 
three bars of each set being used in tension and three in com- 
pression. 
Bars of iron of like dimensions were also tested in the same 
way, in order to obtain the relative effects in steel andiron, In 
these experiments sixty-seven steel bars were tested whose tensile 
strength varied from 32 to 53 tons per inch, and twenty-four iron 
bars varying from 22 to 29 tons per inch. 
The amount of the extensions and compressions were ascer- 
tained by direct measurement, verniers being for this purpose at- 
tached to the bar itself, 10 ft. apart, so that the readings gave 
the absolute extensions and compressions of this length of the 
bar. 
These experiments, which were very accurately made, showed 
that the extension and compression of steel per ton per inch was 
a little less than wrought-iron, that the extension and compres- 
sion were very nearly equal to each other, and that the modulus 
of elasticity of steel may be taken at 30,000,000, which result 
agrees withthe conclusions arrived at by American engineers on 
this subject. : 
This property of the metal is important in two respects. First, 
because inasmuch as the extension per ton per inch is practi- 
cally equal to the compression, it follows that the neutral axis of 
a structure of steel, strained transversely, will be in the centre 
of gravity of its section, and that the proper proportion to give 
to the upper and lower flanges of a girder, when made of the 
same quality of steel throughout, will be the same as in wrought- 
iron. Secondly, because the modulus of elasticity of steel is 
practically equal to that of wrought-iron, and the limit of elas- 
ticity is greater, it follows that in a girder of the same proportions 
as wrought-iron, and strained with an equal proportion of its 
ultimate tensile strength, the deflection will be greater in the 
steel than in the iron girder, in the rate of the strength of the 
metals ; so that if it is necessary to make a steel girder for a 
given span deflect under its load the same amount as an iron 
aoe of the same span, thesteel girder must be made of greater 
epth, 
The fourth series of experiments were made by the Committee 
on riveted steel, and show clearly that the same rules which 
