A book of bridges

by Walter Shaw Sparrow

It is risky at the present time to say that a bridge has certain old characters: change is so rapid that no pontist can keep in touch with its vagaries; but I believe the old bridge at Bâle is alive, and that it keeps in use the Gothic tower, a triangular defence of red sandstone erected on the middle pier, and devoted now to a thermometer, a barometer, and a table of weights and measures. Laellenkoenig has gone, of course, and Bâle junior has grown much bigger and less techy.

The Bridge of Sighs, at Venice, must be included among the exceptional bridges, being equally celebrated in history and in art. Who can say how many times she has been etched and painted and engraved? She is not very important as a work of architecture, yet artists are drawn towards her invariably, and seldom do they fail to make her impressive. Brangwyn loves the Bridge of Sighs, and does her much more than justice in one of his finest etchings. There is something trivial in her Renaissance ornament, and her proportions are not great, being only two metres wide and six high; on the other hand, her abutments are famous buildings, the ducal palace and the State prison. It is from the second storey of the palace that we enter the gloom of her covered passage, concerning which a Frenchman writes as follows: “On pourrait presque le comparer, en agrandissant les proportions, à nos fourgons d’armée.”

It is said that only a prisoner here and there went over this bridge more than once—in his compulsory walk from a dungeon in the prison to the Council of the Ten. Those who awaited their trial in the dungeons were looked upon as already condemned; their appearance before the Ten was a formality, at least in public opinion; and for this reason the dark corridor across the canal was called the Bridge of Sighs.

Among the bridges of the fourteenth century there are two that history has set down as very exceptional. One of them is a covered bridge over the Ticino at Pavia, erected under the care of Gian Galeazzo Visconti. Professor Fleeming Jenkin says of it: “This bridge, which still exists, has seven pointed brick arches, each 70 ft. in span and 64 ft. in height; the depth of the arch ring at the crown is 5 ft. 6 in. The tympanum is pierced; the bricks used in the arches are formed to suit their position, and are hollow in the middle to diminish the weight. The roof of the roadway is carried by a hundred rough granite columns.”

This neat description is accurate, but in it the bridge is not visualised. Would that we had a Brangwyn sketch! I have by my side an engraving of the bridge, and the effect of the design is that of an open-work frieze. Each gracefully pointed arch is a repetition of the other six; the piers also are uniform and graceful, being all 16 ft. 3 in. wide; and all the spandrils are pierced in the same triangular fashion. The point of each triangle is turned downwards, its sides are the inner surfaces of two arch rings, and its base, turned upwards, and gracefully arched with seventeen long bricks, helps to support the parapet. On this parapet at equal intervals rise the hundred granite columns by which the covered roadway is carried. So the design is a clever feat not merely of repetitive decoration, but of repeating solids and voids that oppose each other in a harmony of contrasts; for the empty spandrils in their form oppose the leaf-shaped openings made by the arches, and all the curved solids of the bridge are foiled in a rugged manner by the upright columns, as well as by the long horizontal lines of the covered roadway. In the contrast between cold granite and warm brick there is colour also, and it suits the pulsating light and heat of Italy.

As for the second bridge of the fourteenth century, which architects regard as very uncommon, it exists in drawings only, for it was destroyed by Carmagnola. Its founder was a duke of Milan, Bernabò Visconti, and it crossed the Adda at Trezzo. According to Hann and Hosking, it had “a single arch of granite, very well constructed of stones in two courses, the innermost 3¼ ft. thick in the direction of the radius, the outermost 9 in., the span at low water 251 ft.; the river rises sometimes 13 ft.” The radius of the arch was 133 ft. A span of 251 ft. in a stone bridge was a noble achievement. It is the largest that I remember. The Grosvenor Bridge at Chester has a span of 200 ft., just thirty yards wider than the central arch of Trajan’s Bridge over the Tagus. New London Bridge in her finest arch attains a span of 152 ft., beating Waterloo Bridge by nearly eleven yards. Two French bridges of the eighteenth century—the Pont de Lavaur and the Pont de Gignac—have spans of 160 ft.; and let me refer you also to the Pont de Neuilly-sur-Seine ([p. 338]).

Many uncommon bridges have been attributed to the Chinese, and I know not what to say about some of them. Let me quote from Marco Polo, giving also the excellent notes written by his editor Colonel Yule. In the twenty-seventh chapter of his travels Marco Polo speaks “of the river named Pulisangan, and of the bridge over it.” This river, whose name is written variously, is believed to be the Hoen-ho of the Jesuits’ map, which, uniting with another stream from the north-west, forms the Pe-ho or White River. When Marco Polo comes to the Pulisangan[129] he finds “a very handsome bridge of stone, perhaps unequalled by another in the world.” “Its length is three hundred paces, and its width eight paces; so that ten men can ride abreast without inconvenience.[130] It has twenty-four arches, supported by twenty-five piers erected in the water, all of serpentine stone, and built with great skill. On each side, and from one extremity to the other, there is a handsome parapet, formed of marble slabs and pillars arranged in a masterly style. At the commencement of the ascent the bridge is something wider than at the summit, but from the part where the ascent terminates, the sides run in straight lines and parallel to each other.[131] Upon the upper level there is a massive and lofty column, resting upon a tortoise of marble, and having near its base a large figure of a lion, with a lion also on the top.[132] Towards the slope of the bridge there is another handsome column or pillar, with its lion, at the distance of a pace and a half from the former; and all the spaces between one pillar and another, throughout the whole length of the bridge, are filled up with slabs of marble, curiously sculptured, and mortised into the next adjoining pillars, which are, in like manner, a pace and a half asunder, and equally surmounted with lions, [133] forming altogether a beautiful spectacle. These parapets serve to prevent accidents, that might otherwise happen to passengers. What has been said applies to the descent as well as to the ascent of the bridge.”[134]

I do not understand why this description is considered very difficult to understand. It depicts a gabled bridge with a flat top, not an uncommon form of bridge in China, I believe. The footway ascends to the beginning of the middle arch, where it becomes flat and level; it continues so for the full width of the arch, and then it descends toward the abutment across the river. With this picture in mind it is easy to decorate the bridge over the Pulisangan, or Hoen-ho, with the accessories described by Marco Polo. The parapets have coping stones of sculptured marble, and pillars are carefully set along the parapets at an equal distance from each other. These pillars are of two sorts. Those above the flat part of the roadway, where the parapets also are horizontal, are tall and massive. On each side, at the brow of the ascent, there is a tall pillar upon the summit of which is a stone lion; and in the middle of each parapet, on this level part of the road, there is a taller and heavier column, whose pedestal is a marble tortoise, and whose summit carries a symbolic lion. Another lion is placed near the tortoise, perhaps on a ledge of stone corbelled out from the parapet. As for the parapets that slope up from the abutments to the point where they become level, or horizontal, they, too, have their emblematic lions carried by pillars, and these ornaments, in accordance with the logic of design, are much smaller than those on the summit of the steep bridge. For the rest, Marco Polo speaks of twenty-four arches and of twenty-five piers; and if we give to the arches an average span of fifty-two feet, and to the piers an average width of thirteen feet, we get a bridge 1573 ft. long, or seventy-three feet longer than the five hundred yards suggested by Colonel Yule. Viewed in this way, apart from the vague glamour of enthusiastic words, there is nothing extravagant in Marco Polo’s description.

Many writers have been astonished by another Chinese bridge, called the Bridge of Cho-gan, in the province of Shen-si. Its great arch is said to have had an unrivalled span. I am told that it was built with huge blocks of stone, cut into voussoirs, the joints of which converged towards a common centre, as in our own bridges. This may be true, though in photographs of Chinese bridges which I have seen the voussoirs do not resemble ours; not only are they much longer, they are much narrower also, and recall to my memory a good description written by Barrow, whose impressions of China are invaluable to students. Barrow speaks of archstones from five to ten feet long, and says that each stone “is cut so as to form a segment of the arch.” “There is no keystone” when an arch is built in this manner. Again, “ribs of wood fitted to the convexity of the arch are bolted through the stones by iron bars, fixed in the solid part of the bridge”; sometimes no wood is employed, and then “the curved stones are mortised into long transverse blocks of stone.” It would be ridiculous to speak of this technical method as one that employs voussoirs, since the arch ring is built with a few segmental stones and without a keystone; and possibly the Bridge of Cho-gan was constructed in this fashion. A drawing of it is given in Kircher’s “La Chine Illustrée”—or, rather, in Dalquié’s translation of Kircher’s book, published in 1670 at Amsterdam. It is not a geometrical drawing, and the dimensions are given in Chinese measures, which do not help us to love Kircher and Dalquié. M. Degrand is baffled by these measures;[135] but he admits that the Bridge of Cho-gan must have been a grandiose structure dating from a very remote time.

Gauthey speaks with admiration of the “Pont de Fo-Cheu sur le Min”—a bridge not less than 7935 metres long by 19 metres 50 wide, with a hundred arches, all semicircular, and thirty-nine metres in their average span. The piers were nearly as broad, and their height was thirty-nine metres. Here is a bridge that Dean Swift ought to have put into his pictures of Brobdingnag. Gauthey seems to have faith in it, while M. Degrand has doubts. He says: “Even if we admit that there is no flagrant exaggeration in the documents from which the account of this bridge is taken, the workmanship in its general character, as shown in the drawing given by Gauthey, has a near resemblance to that in Roman bridges, and ought not to be assigned to a period earlier than theirs.” Gauthey describes the decorative treatment. Under the parapet of white marble ran a line of consoles; the piers were surmounted by figures of lions in black marble, cut from blocks seven metres long; and above each twentieth arch the footway was guarded by a gateway, un arc de triomphe.