Chapter 19: Transporter Bridges

When the writer was in Rouen, in 1898, two lofty iron towers were being constructed by the Seine: the one on the Quai du Havre, the other on the Quai Capelier, which borders the river on the side of the suburb St. Sever.

The towers rose so far towards the sky that one had to throw one’s head very far back to watch the workmen perched on the summit of the framework. What were the towers for? They seemed much too slender for the piers of an ordinary suspension bridge fit to carry heavy traffic. An inquiry produced the information that they were the first instalment of a “transbordeur,” or transporter bridge. What is a bridge of this kind?

Well, it may best be described as a very lofty suspension bridge, the girder of which is far above the water to allow the passage of masted ships. The suspended girder serves only as the run-way for a truck from which a travelling car hangs by stout steel ropes, the bottom of the car being but a few feet above the water. The truck is carried across from tower to tower, either by electric motors or by cables operated by steam-power.

The transporter bridge in a primitive form has existed for some centuries, but its present design is of very modern growth. With the increase of population has come an increased need for uninterrupted communication. Where rivers intervene they must be bridged, and we see a steady growth in the number of bridges in London, Paris, New York, and other large towns.

Unfortunately a bridge, while joining land to land, separates water from water, and the dislocation of river traffic might not be compensated by the conveniences given to land traffic. The Forth, Brooklyn, Saltash, and other bridges have, therefore, been built of such a height as to leave sufficient head-room under the girders for the masts of the tallest ships.

But what money they have cost! And even the Tower Bridge, with its hinged bascules, or leaves, and bridges with centres revolving horizontally, devour large sums.

Wanted, therefore, an efficient means of transport across a river which, though not costly to install, shall offer a good service and not impede river traffic.

Thirty years ago Mr. Charles Smith, a Hartlepool engineer, designed a bridge of the transporter type for crossing the Tees at Middlesbrough. The bridge was not built, because people feared that the towers would not stand the buffets of the north-easterly gales.

The idea promulgated by an Englishman was taken up by foreign engineers, who have erected bridges in Spain, Tunis, and France. So successful has this type of ferry-bridge proved, that it is now receiving recognition in the land of its birth, and at the present time transporter bridges are nearing completion in Wales and on the Mersey.

[Illustration: THE LATEST TYPE OF BRIDGE

The Transporter Bridge at Bizerta, Tunis. It has a span of 500 feet, and the suspension girder is 120 feet above high water, so that the largest vessels may pass under it from the Mediterranean to the inland lakes. The car is seen near the bottom of the right-hand tower.]

The first “transbordeur” built was that spanning the Nervion, a river flowing into the Bay of Biscay near Bilbao, a Spanish town famous for the great deposits of iron ore close by. A pair of towers rises on each bank to a height of 240 feet, and carry a suspended trussed girder 530 feet long at a level of 150 feet above high-water mark. The car, giving accommodation for 200 passengers (it does not handle vehicles), hangs on the end of cables 130 feet long, and is propelled by a steam-engine situated in one of the towers. Motion is controlled by the car-conductor, who is connected electrically with the engine-room. The lofty towers are supported on the landward side by stout steel ropes firmly anchored in the ground. These ropes are carried over the girder in the familiar curve of the suspension bridge, and attached to it at regular intervals by vertical steel braces. The cost of the bridge--£32,000--compares favourably with that of any alternative non-traffic-blocking scheme, and the graceful, airy lines of the erection are by no means a blot on the landscape.

The second “transbordeur” is that of Rouen, already referred to. Its span is rather less--467 feet--but the suspension girder lies higher by 14 feet. The car is 42 feet long by 36 broad, and weighs, with a full load, 60 tons. A passage, which occupies 55 seconds, costs one penny first class, one halfpenny second class; while a vehicle and horses pay 2-1/2d. to 4d., according to weight. The car is propelled by electricity, under the control of a man in the conning-tower perched on the roof.

At Bizerta we find the third flying-ferry, which connects that town with Tunis, over a narrow channel between the Mediterranean Sea and two inland lakes. It replaced a steam-ferry which had done duty for about ten years.

The lakes being an anchorage for war vessels, it was imperative that any bridge over the straits should not interrupt free ingress and egress. This bridge has a span of 500 feet, and like that at Bilbao is worked by steam. Light as the structure appears, it has withstood a cyclone which did great damage in the neighbourhood. It is reported that the French Government has decided to remove the bridge to some other port, because its prominence would make it serve as a range-finder for an enemy’s cannon in time of war. Its place would be taken either by a floating-bridge or by a submarine tunnel.