A book of bridges

by Walter Shaw Sparrow

A bridge here and there is supposed to be all right. Take, for instance, the Forth Bridge, with his 51,000 tons of steel, and his amazing cost, about £3,000,000; he is looked upon as a “safe” bridge, and safe he is if we forget what bombs and shells can do in a few seconds. At each end of this bridge the railway is carried by trivial columns forming the approach viaducts, and these a naval gun would blow to smithereens. A bomb falling upon them from an airship might put the whole bridge out of action. Further, the columns are comically out of scale with those gigantic pyramids of steel bars which counterbalance the centre girders, and yet seem to play at leapfrog in two bounds of 1710 ft. each, and in two lesser jumps of 680 ft. each. Yes, the Forth Bridge looks formidably alive and active; he is to modern engineering what the Ichthyosaurus became to our knowledge of prehistoric animals: a semi-marine colossus, fit to be kept for ever as a tremendous danger happily extinct.

Several years ago, in the “Builder,” I drew attention to the defenceless character of this huge viaduct over a strategic waterway, and now I return to this topic at the beginning of a war that may well be the most terrible in all history. To-day is the 3rd of August, 1914; and the world knows that Germany has occupied Luxemburg, a neutral State, has poured her troops into Belgium, the naval key of Great Britain, and has violated the French frontier without declaring war. Here is the swift “morality” of lightning. In the strategy of war, non-moral Powers may gain over us a horrible advantage. England talks so much about peace and honour that felon Germany is able to plan at her ease great military movements of surprise as fateful as victories on stricken fields. Before this little book is published “the black bullets of Destiny” will have been cast in several countries; and not a battle will be won, nor a skirmish fought, without either help or hindrance from those soldiers unprepared that we call viaducts and bridges. Already many have been blown up in Belgium and in Servia; and by night and day, throughout Europe, men are trying to guard every bridge of vital importance to the concentration of troops. Here in England this protection is not always as alert and thorough as it ought to be. I am writing in Hampshire, near by the main line from Aldershot; within a walk of three minutes there is a high railway bridge over a road, and a few hours ago it was unguarded from the road. Yesterday evening, after dark, a German spy could have destroyed it, for I passed under its vault and found no one keeping watch and ward.[144] Instead, I encountered that supine national folly which has withheld our young men from national service, because of the rich liberty which we are supposed to get somehow from cooing claptrap, and Norman Angells, and the future pacification of mankind.

Whatever this fateful war may bring to us and to others, the defenceless bridge will have to be reconsidered; and for this reason its evolution attracts me even now, despite the darkling uncertainty that encompasses every hour of the day. The Forth Bridge, all shatterable bulk and no beauty and grace, does full justice to our industrialism, but yet he belongs, not to the public spirit of Great Britain, but to the spirit of the age everywhere; for in other lands he has a great many rivals not a whit less huge and vulnerable. As an example, we will take the Illinois and St. Louis Bridge, really a fine work of his kind, dating from 1873. He crosses the Mississippi, which at St. Louis flows in a single channel 534 yards wide and 8 feet deep at extreme low water. The greatest range between high and low water is 41 feet. There are three ribbed arches of cast steel, the middle one with a span of 520 feet, while the others are 18 feet narrower. If it was worth while for the sake of public convenience to erect this great highway above a wide and dangerous river, it was also worth while for the sake of public convenience that the width of the arches should be determined by the probable dangers to which the bridge would be exposed in commercial strikes and in other wars. Human gunpowder is not a rare thing in the United States of America. The black race there has a population that increases rapidly, and some day it may breed a great soldier, a dark Napoleon, who will find it no difficult task to organise a widespread society of bridge-wreckers. No truisms are more common than unexpected events. Let us then ask whether it would be possible swiftly to repair a metal arch having a span of 520 feet. If not, why build a huge and costly structure with steel-ribbed arches which are much too wide? What if one of them was destroyed at a time when the double railway track over the river, and the wide roadway above for other traffic, were necessary to bring reinforcements to a stricken army?

ON THE TARN AT MILLAU IN SOUTHERN FRANCE. THIS DRAWING, A COMPANION PICTURE TO GIRTIN’S “BRIDGNORTH,” REPRESENTS THE BROKEN END OF AN OLD BRIDGE WITH A MILL BUILT ON IT; BEHIND IS AN ARCH OF THE NEW BRIDGE

These questions were too unmercantile to be considered by the chief engineer, Captain James B. Eads, a very scientific person, who was entirely of a piece with our European pontists. Not a scrap of attention did he pay to military matters. Every account of Captain Eads and his bridge bombards us with technical details. We are expected to gape with admiration because £60 per ton of 2000 lbs. was the price paid for 2500 tons of cast-steel. Wrought-iron in a ton of 2000 lbs. cost £40, and 500 tons at this price were used. Rolled-iron in a ton of 2000 lbs. cost £28, and 1000 tons at this price were employed, together with 200 tons of cast-iron at £16 per ton, the ton in this case being 2240 lbs. Here indeed is a golden target for bombs and for modern artillery!

Every bridge in the United States of America is a target of this sort in one form or another. There are bonfire timber bridges, for example, exceedingly deft and excessively high; sometimes their piers are nothing more than large wooden frames piled one on top of another, up and up and up, till at last they are tall enough to be known as great sky-ticklers. One example is 234 feet high. It is the great Portage Bridge spanning the Genesee River, in the State of New York, on a railroad between New York and Buffalo. It looks like a miracle of carpentry, this wonderful bridge of frames; its length is 240 metres, and the piers—sixteen romantic scaffoldings—form immense triangles with flattened summits upon which a double gallery rests as a firm support for the railway. Each scaffolding rises from a pile of masonry nine metres higher than water-level, so that floods do not break their force against the timber frames. Good heavens above, how this bridge would burn! But it has a quite modern fascination: its cost of production was cheap!—cheap in comparison with the estimated price of a stone bridge with the same length and aviated height. This wooden structure cost about £36,000, for the pride of trade likes to pay as little as possible for the largest amount of very perishable insecurity.

Then, of course, there are sky-tickling metal bridges, and these spindle-shanked devotees of peace are popular also in Canada. All this work is nothing but industrial engineering, like the mighty bridges at New York, though these do try to look somewhat architectural. One specimen, indeed, a vast structure called the New Manhattan Bridge, has marvellously long suspension cables which do not go through a tower or gateway; they actually pass over their supports in a logical manner. What a blessing! On the other hand, Brooklyn Bridge at New York has the same mistake as our suspension bridge at Clifton ([p. 346]); and the pierced towers, each with two lancet-shaped openings, are affected and trivial. Brooklyn Bridge has a total length of nearly 1141 yards, and between the two towers there is a span of 1595 feet. The roadway is upheld by four galvanised steel cables not less than sixteen inches in diameter. Think of that! Try to imagine a span 1595 feet wide! Suppose an airship crippled it with some large bombs, how in the world could repairs be made?

Briefly, then, modern bridges everywhere are anti-social. When war is afoot, they imperil the best-made plans of strategists; and even in strikes they have to be guarded by soldiers, as if they were convents where dethroned queens lived unhappily with suffragette princesses. Though we have lived for many years on the brink of war, every highway in Europe as in America is at the mercy of bridge-wreckers. Is it not dumbfounding that no respect has been paid anywhere to the social guardianship that bridges and roads ought to perform? Why has this all-important matter been forgotten? It has been made memorable a great many times in history, ever since Horatius Cocles and his two companions held the Pons Sublicius against the whole Etruscan Army under Porsena,—a lesson never forgotten by Roman citizens.