F. M. Holmes

“ Standing on the platform at King’s Cross, with a large part of the immense driving-wheel hidden below you as it rests on the rail, you do not realise its tremendous size. Yet, let the engine-driver open the throttle, as it is called—that is, turn on the steam to the cylinders—and that huge wheel will revolve, and with its neighbour on the other side, haul after them that heavy train of carriages, and, gathering speed as they go, they will soon be rushing up the incline at forty miles an hour, and then on at sixty. ”

“ But before lattice girder bridges had become so popular, another class had come into use, and afford some splendid specimens of engineering skill. These are suspension bridges, and, perhaps of all kinds, they are the most picturesque. Their graceful sweeps and curves yield perhaps a more pleasing sight for the eye than the solid, rigid, straight lines of the girder bridges.
It was the genius of Thomas Telford which gave a great impetus to this class of bridge. Like Stephenson after him, he had to bridge the surging Menai Straits, but for a carriage road, not a line of rails ”

“ Indeed, although Savery and Newcomen and others are entitled to great praise, it was Watt who gave it life, so to speak, and made it, in principle and essence, very much that which we now possess. There have, indeed, been improvements as to the boiler, as to expansive working, and in various details, since his day; but, apart from the distinctive forms of the locomotive and the marine engine, the machine as a whole is in principle much as Watt left it.
The centre of all things in a steam engine is usually the cylinder. ”

“ At all events, the development of the steamboat made practically no progress [59] until Symington commenced his experiments under Lord Dundas.
Russell is of opinion that the invention of steam navigation was the joint production of these three men. “The creation of the steamship,” says he, “appears to have been an achievement too gigantic for any single man. It was produced by one of those happy combinations in which individuals are but tools, working out each his part in a great system, of the whole of which no single one may have comprehended all the workings.” ”

“ For days and nights the fires are kept at glowing heat. A forced blast maintains the draught; the steam condensed back into warm water is supplied to the boilers; half-naked men work hour after hour to rake the fires, clean them, pile on the fuel, and keep the most powerful head of steam the boilers can stand.
When the furnace doors are opened tongues of flame leap forth, and the heat is enough to make a man sick. ”

“ A modern steamship, with its multitude of comforts and conveniences for passengers and its complexities of machinery for fast and safe steaming, is a great triumph of engineering skill. Patience and forethought, the persevering development of sound principles, and the application of new ideas, have all contributed to this great achievement.
From the Comet to the Campania is a marvellous development within a century. ”

“ The locomotive had now become one of the wonders of the world. Since then its speed has been doubled. But all the improvements (with possibly one exception—that of the compound cylinder which is at present only partially in use) have been more in details than in principles. Thus the 70 or 80 ton express engine, which covers mile after mile at the rate of a mile a minute without a wheeze or a groan, is not very different essentially from George Stephenson’s locomotives, though its steam pressure is very much higher. ”

“ He connected the cylinder of an engine with a separate vessel, in which the air was exhausted, and found that his idea was correct; the steam did rush into it. Consequently the steam could be condensed in a separate vessel, and the heat of the cylinder maintained and the loss of power prevented. This invention seems simple enough; yet it increased the power of an engine threefold, and is at the root of Watt’s fame. We must remember that the inventions which in process of time may [24] appear the simplest and the most commonplace, may be the most difficult to originate. ”

“ Now, in its simplest form, a suspension bridge has been known for ages. It is merely a pathway, or even a small movable car, suspended from a rope or ropes across a chasm. Ulloa describes suspension bridges built by the Peruvians in South America. Four stout cables span a river, and on these four is placed the platform of sticks and branches, while two other ropes connected with the platform are useful as hand rails. Such bridges sway with the wind and move with the passenger, but for light loads they appear to be perfectly safe. ”

“ Then coal has to be brought from the bunkers to the furnaces, tons of it per day, and if the ship rolls too much for the barrows to be used, the fuel must be carried in baskets.
There is an engineer in charge of each stoke hole, and two on the platform in each engine room; as a rule, the staff are on duty in turns—four hours out of every twelve. But if the weather be bad they may have harder times.
No matter how hot the machinery becomes, the engineers must not reduce speed, except it be to prevent disaster. ”

“ Not long afterwards Stephenson became satisfied that chains were not needed to assist in supporting the bridge, and that his tubes would be strong enough to support themselves entirely between the piers.
Work therefore went forward. Some 1500 men were engaged on the Britannia Bridge, and the quiet shores of the Menai Straits resounded with the busy hum of hammers and machinery. Cottages of wood were built for the men, and workshops for the punching and rivetting of the plates for the gigantic tubes. ”

“ Passing by the fact that it is evidently safer to span a swelling river by a bridge of wide, rather than of several narrow arches, three powers or forces act on the row of stones or bricks forming the arch. There is first the force that would carry the stone downward—that is, the force of its own weight and of anything that might be placed upon it. ”

“ In principle, the sinking of the shaft was conducted much as Brunel’s shaft at the Thames [158] Tunnel, only it was built up of iron instead of brick. Imagine a big gasometer with a scaffold near the top, where men are busy building the walls higher and higher by adding on plate after plate of iron. On reaching the scaffold you find that there are two great cylinders of iron, one standing inside the other, and concrete is being filled in between them. Men also are down below digging out the earth which is being swung up in iron buckets ”

“ Robert Stephenson—for he it is whom we suppose to be speaking to his friend on this gigantic engineering enterprise—became satisfied by reflection that the principles involved in constructing an immense tubular beam were but a development of those commonly in use; and Sir William Fairbairn was entrusted with the duty of experimenting as to the strength of tubes, the directors of the Railway Company voting a sum of money for the purpose. ”

“ The improved explosives and rock-drills have gone further.
Even as the Mont Cenis shows a transition period, so the Arlberg may be said to emphasise a triumph of the methods then indicated. So great have been the improvements of the rock-boring machinery, of the power of the blasts, and the speedy ventilation following the explosions, and of the quick transit of materials, that we shall most likely hear no more of sinking numerous shafts along the route.
But what of subaqueous tunnels? Violent explosives are hardly suitable for excavation a few feet under a turbid river. ”

“ Why, then, did not Stephenson construct a similar bridge when, twenty years or so later, he had to solve a similar problem?
The answer is, that suspension bridges are not—or were not—considered sufficiently strong and rigid for railway work. In America, however, they have been used for this purpose; witness the famous Niagara Suspension Bridge, 21⁄3 miles below the Falls, and [123] with a superb span of 822 feet; but American engineers appear to stiffen the roadway considerably, so as to distribute the stress of the rushing train over a large portion of the cable. ”

“ It is done—dampers are clapped on furnaces, steam pressure dropped a little, and engines reduced to half speed; the three great cranks of the high, intermediate, and low pressure cylinders move round easily, and the tremendous noise gradually sinks to a murmur, compared with the previous rush and roar. The machinery cools. But when quite safe, on is piled the speed once more, and again the cranks fly round, and the mighty engines work their hardest to drive the mammoth ship through the surging green rollers. ”

“ Placed between the front wheels, the bright boss of this cylinder may be seen in shining steel as it flies over the rails.
The argument is that the compound burns less fuel and is more powerful than a non-compound of the same weight; but against this is launched the objection that the compound is more expensive to build, to repair, and to maintain. Still further it is argued, that a fast-speeding locomotive has not the time in its hurrying life to expand its steam in the tick of time between each stroke of the piston. ”

“ In the Tower Bridge there are two of such huge “flaps” or leaves, each about 100 feet long, one rising and falling from each pier and meeting in the centre. Large bascule bridges are usually constructed in this manner, and there is an excellent specimen over the Ouse, for the passage of the North-Eastern railway; one man at each half of the bridge can raise it in less than two minutes. Another fine bascule may be seen at Copenhagen.
The bascules are raised and lowered by chains, which, in the case of the Tower Bridge, are worked by superb hydraulic power from the massive pier towers. ”

“ The wheels, though smooth, kept to the rails, though they were smooth also, and the framework went along without slipping. ‘Crikey!’ says Hedley, ‘no cogged wheels, no chains, no legs for me! We can do without ’em all. Smooth wheels will grip smooth rails.’ And he proved it too by several experiments.”
“Then Mr. Blackett had this engine built?”
“Ay, and it be, as you say, a great improvement. But that steam blowing off there, after it have done its work, frights the horses on the Wylam Road ter’ble, and makes it a perfect nuisance.” ”

“ Another difficulty with which Trevithick had to contend was one of cost. It is said that one of his experiments failed in London for that reason. This was apparently the locomotive for roads, as distinct from the locomotive for rails. A machine may be an academic triumph, but the question of cost must be met if the machine is to become a commercial and industrial success.
Mr. Blenkinsop of Leeds then took out his patent in 1811 for a rack-work rail and cogged wheel; but before this Mr. Blackett of Wylam had obtained a plan of Trevithick’s engine and had one constructed. ”

“ Even so great a philosopher as Dr. Lardner could not believe in 1835 that a steamship could voyage from Liverpool to New York without stopping—we presume for fresh fuel.
The Great Eastern, therefore, was planned to carry 15,000 tons of coal; whereas now the large Atlantic liner Paris needs only 2700 tons for her Atlantic trip. The difference is most striking, for the Paris is one of the largest steamships afloat, but her working steam pressure is 150 lbs. instead of the 15 or 25 lbs. ”

“ The use of the steam expansively is to stop its rush to the cylinder when the piston has only partially accomplished its stroke, leaving the remainder of the [22] stroke to be driven by the expansion of the steam. In early engines the steam was admitted by conical valves, worked by a rod from the beam. Murdock, we may add in parenthesis, is believed to have invented the slide-valve which came into use as locomotives were introduced, and of which there are now numerous forms. The valve is usually worked by an “eccentric” rod on the shaft of the engine. ”

“ The locomotive needed something more, some magic touch to render it less clumsy and more effective. What was it?
Then came the first great practicable improvement after the smooth wheels on smooth rails. It was the steam-blast in the funnel, by which the draught in the furnace was greatly increased. Indeed, the faster the engine ran the more furiously the fire would burn, the more rapid would be the production of steam, and the greater the power of the engine. ”

“ Then there is greater wear and tear on paddle-wheels, and consequently the screw vessels are less expensive. But most important of all, the screw being deep in the water, the vessel is much more suitable for ocean traffic. In the heaving billows of the sea one wheel may be buried deep on one side of the ship, and the other whirling round high in the air, and not propelling the vessel; whereas the screw, being always immersed, except possibly in severe pitching, is more constantly efficient for the whole of the vessel. ”

“ Thus William Hedley’s idea of trusting to the weight of the engine to grip the rails, and abolishing all the toothed wheels and legs and rack-work for this purpose on a fairly level rail, was the first great step toward making the locomotive a practicable success. ”

“ The old Hungerford Bridge stood here previously, and its two piers of brickwork were used for the new bridge. Other piers are huge cylinders of cast iron ten feet across, but fourteen feet in diameter in the ground. Thus they are broadly based. These piers are filled with concrete and also brickwork, and are topped with bearing-blocks of granite. They are formed of plates of cast iron bolted together, and they were sunk into the ground many feet below high-water by combined forces; divers scooped out the mud and gravel and clay from within the cylinders ”

“ It is not a little curious to note how, in many of these great undertakings, several minds seem to have been working to the same end at about the same time. It was so with George Stephenson and others with regard to the locomotive, with Miller and Symington, Bell and Fulton, with regard to the steamship, with Laird and Brunel as regards transatlantic steam navigation, with Robert Stephenson and William Fairbairn as regards the tubular bridge. ”

“ Between the piers the weight of the structure, including the chains, amounts to nearly a thousand tons.
In all these suspension bridges, however large, the principles are much the same. The platform, or roadway, is hung from chains or cables, which pass over piers and are anchored fast at the ends. Some are stiffened with girders and bracing to prevent undue undulation. The chains take a graceful and definite curve, that of the Menai Bridge dipping fifty-seven feet. The strain is the greatest at the lower part, and is increased, should the chain be drawn flatter over the same space. ”

“ About 4000 tons of water an hour pass through the surface condensers of a large liner when she is at full work.
The largest steamers require over 150 men to work the furnaces and machinery, and the attention given is hard and unremitting. In some of the fast Atlantic greyhounds the strain is terribly severe, especially when the sea is beginning to run high. The rollers may be but 20 feet, yet these are quite high enough even for a splendid ocean racer to contend with and yet maintain her speed. ”