36 



NATURE 



[Nov. 14, 1889 



viscosity" ; tempering is the release of this molecular 

 strain by heat. 



Highly carburized steels harden very energetically by 

 very slight modifications in thermal treatment, and it will 

 be evident that a very hard material is unsuitable for 

 industrial use if the conditions of its employment are such 

 as to render it desirable that the material should stretch. 

 To turn to very " mild " steel which does not harden, it 

 is certain that, although wrought iron passes almost 

 insensibly into steel, there can be no question that not 

 merely the structural but the molecular aggregation of 

 even steel containing only j-g per cent, of carbon is 

 profoundly different from that of wrought iron. Formerly, 

 as Sir F. Bramwell pointed out in a lecture delivered at 

 the Royal Institution in 1877, "by the year 1830 . . . from 

 small beginnings in Staffordshire and at Birkenhead 

 sprang a wonderful wrought-iron navy, but steel was a 

 luxury : it was made in small portions sold at high prices, 

 as much as a shilling or eighteenpence a pound. It was 

 employed for swords, cutlery, and tools, needles and other 

 purposes where the quantity used was but trifling, and 

 where the importance of the superior material was such 

 as to justify the large expenditure incurred. It was felt 

 in those days that steel was worth paying for because it 

 was trusted ; indeed its trustworthiness had passed into 

 a proverb " — " as true as steel." 



The class of steel which was formerly employed, as I 

 have just indicated, for weapons and tools belonged to 

 the highly carburized, readily-hardening class. It was 

 the " mild steel " containing but little carbon which was 

 destined to replace wrought iron, and when attempts were 

 made to effect the general substitution of steel for iron, 

 fears as to its character and trustworthiness unfortu- 

 nately soon arose, so that from about the year i860 

 until 1877 steel was viewed with suspicion. We can now 

 explain this. Doubts as to the fidelity of steel, even when 

 it was obtained free from entangled cinder, arose from 

 ignorance of the fact that, on either side of a com- 

 paratively narrow thermal boundary, the iron in steel can 

 practically exist in two distinct modifications. The steel 

 was true enough, but from the point of view of the special 

 duties to be intrusted to it, its fidelity depended on which 

 modification of iron had to be called to the front. 

 Artificers attempted to forge steel after it had cooled 

 down below the point a of Chernoff, at which recal- 

 escence occurs, and they often attempted to work highly 

 carburized steel at temperatures which were not sufficiently 

 low. 



Steels may be classified from the point of view of their 

 industrial use according to the amount of carbon they 

 contain, and I have attempted to arrange in this trophy 

 certain typical articles, grouped under certain definite 

 percentages of carbon ranging from ^^^ to \\ per cent. 

 [This was a trophy 18 feet square, with various typical 

 articles of steel arranged in order according to the 

 amount of carbon they contained. I am greatly indebted 

 to Mr. J. W. Spencer, of Newcastle, who kindly lent me 

 the fine series of specimens of which the "trophy" is 

 built up.] Each class merges into the other, but the 

 members at either end of the series vary very greatly. 

 It would be impossible to make a razor which would cut 

 from boiler plate ; and conversely, a boiler made of razor 

 steel would possibly fracture at once if it were super- 

 heated and subjected to any sudden pressure of steam. 

 Speaking generally, if the steel contains, in addition to 

 carbon, y© per cent, of manganese, each class of steel, as 

 at present arranged, would have to be shifted a class 

 backwards towards the left of the trophy. 



At the present day, instead of steel being manufactured 

 and used in small quantities, about 4,000,000 tons are 

 annually employed in this country. Let us see how it is 

 used. A steel fleet, the finest fleet in the world, has 

 recently assembled at Spithead. The material of which 

 it was made contained y'jfjj to ^ per cent, of carbon, and 



when steel faces are used for the armour plates, the 

 material contains f^j to ^^^ per cent, of carbon. 



It has been pointed out that the crews of the fleet at 

 Spithead numbered no less than 21,107 men. This it has 

 been shown is " a remarkable figure, considering the great 

 economy in men which prevails in a modern navy as com- 

 pared with the navy of Nelson's day. A hundred years 

 ago the normal requirements of a fleet were one man to 

 a little over four tons, but now, thanks to the part played 

 by steel and hydraulic power, we require but one man to 

 every seventeen tons. Thus it may roughly be said that an 

 aggregate of 20,000 men at the present day corresponds 

 to an aggregate of 80,000 men in the days of Nelson.'' 

 The latest type of battle-ship weighs, fully equipped, about 

 10,000 tons, there being about 3400 tons of steel in the 

 hull, apart from her armour, which, with its backing, will 

 weigh a further 2800 tons.^ 



From the use of steel in the Royal Navy and in the 

 mercantile marine, let us pass on to its most notable use 

 in construction. If the President of the French Republic 

 was justified in appealing, in a recent speech, to the Eiffel 

 Tower as " a monument of audacity and science," ^ what 

 are we to say of the Forth Bridge, the wonders of which 

 will be described by Mr. Baker on Saturday ? By his 

 kindness I am able to place in the position in the trophy 

 justified by the carbon it contains, a plate from the Forth 

 Bridge, which fell from a height of some 350 feet, and, 

 being of excellent quality, doubled itself on the rocks 

 below. A single span of the Forth Bridge is nearly as 

 long as two Eiffel Towers turned horizontally and tied 

 together in the middle, and the whole forms a complicated 

 steel structure weighing 15,000 tons, erected without the 

 possibility of any intermediate support, the lace-like fabric 

 of the bridge soaring as high as the top of St. Paul's. 

 The steel of which the compression members of the 

 structure are composed contains f>;"jj per cent, of carbon 

 and -{•§xi per cent, of manganese. The parts subjected to 

 extension do not contain more than ^^j^ per cent, of 

 carbon.^ 



Time will not permit me to pass the members of each 

 class in review. I can only refer to very few. Steel for 

 the manufacture of pens contains about ^',7 per qqnt. of 

 carbon, and 16 to 18 tons of steel are every week let 

 loose on an unoffending world in the shape of steel 

 pens. 



Steel rails contain from ■,% to y^^ per cent, of carbon, 

 and, in this class, slight variations in the amount of car- 

 bon are of vital importance. An eminent authority, Mr. 

 Sandberg, tells us that in certain climates a variation of 

 y\j per cent, in the amount of carbon may be very serious. 

 The great benefit which has accrued to the country from 

 the substitution of more durable steel rails for the old 

 wrought-iron ones may be gathered from the figures 

 which Mr. Webb, of Crewe, has given me, which show 

 that "the quantity of steel removed from the rails 

 throughout the London and North-Western system by 

 wear and oxidation is about 15 cwt. an hour, or 18 tons 

 a day." 



Gun-steel contains f|j to {\ per cent, of carbon, and it 

 may contain ^'^^ per cent, of manganese. It is in relation 

 to gun-steel that oil-hardening becomes very important. 

 The oil-tank of the St. Chamond Works (on the Loire) 

 is 72 feet deep, and contains 44,000 gallons of oil, which 

 is kept in circulation by rotary pumps, to prevent the oil 

 being unduly heated locally when the heated mass of 

 steel is plunged into it. 



Now with regard to projectiles. To quote some recent 

 remarks of Lord Armstrong,'* " the heaviest shot used in 

 the Victory was 68 pounds, while in the Victoria it will 

 be 1800 pounds; and, while the broadside-fire from the 



* Address by Mr. Baker, Section G, British Association Report, 1885, 

 p. 1182. 



^ Tunes, August 19, 1889. 



3 lournal of the Iron and Steel Institute, 1888, ii; p. 94. 



■* Times, August 3, 1889. 



