This, or something like this, ought to be a question with every man who builds a structure which is meant to outlast him, whether it be a temple of religion or a work of bare utility like this. It so happens that the work which is likely to be our most durable monument, and to convey some knowledge of us to the most remote posterity, is a work of bare utility; not a shrine, not a fortress, not a palace, but a bridge. This is in itself characteristic of our time. It is true of no other people since the Romans, and of none before. Like the Roman remains, the duration of this work of ours will show that we knew how to build. “A Roman work,” we often hear it said of the bridge, and it is in many ways true. It is far beyond any Roman monument in refinement of mechanical skill. It is Roman in its massiveness and durability. It is Roman, too, in its disregard of art, in resting satisfied with the practical solution of the great problem of its builders, without a sign of that skill which would have explained and emphasized the process of construction at every step, and everywhere, in whole and in part, made the structure tell of the work it was doing. There have been periods in history when this æsthetic purpose would have seemed to the builder of such a monument as much a matter of course, as necessary a part of his work, as the practical purpose which animated the designer of the Brooklyn Bridge. It would have seemed so to the engineer of a bridge in Athens in the second century before our era, or to the engineer of a bridge in Western Europe in the thirteenth century of our era. The utilitarian treatment of our monument is as striking and as characteristic a mark of the period as its utilitarian purpose. It is a noble work of engineering; it is not a work of architecture.
The most strictly scientific of constructors would scarcely take the ground that he did not care how his work looked, when his work was so conspicuous and so durable as the Brooklyn Bridge, and he must be aware that a training in scientific construction alone will not secure an architectural result. It is more probable that he looks upon the current architectural devices as frivolous and irrelevant to the work upon which he is engaged, and consoles himself for his ignorance of them by contempt. Architecture is to him the unintelligent use of building material. Assuredly this view is borne out by a majority of the “architecturesque” buildings that he sees, and he does not lack express authority for it. Whereas the engineer’s definition of good masonry is “the least material to perform a certain duty,” Mr. Fergusson declares that “an architect ought always to allow himself such a margin of strength that he may disregard or play with his construction;” and Mr. Ruskin defines architecture to be the addition to a building of unnecessary features. An engineer has, therefore, some warrant for considering that he is sacrificing to the graces and doing all that can reasonably be expected of him to produce an architectural monument, if in designing the piers of a chain-bridge he employs an unnecessary amount of material and adds unnecessary features. But if we go back to the time when engineers were artists, and study what a modern scientific writer has described as “that paragon of constructive skill, a Pointed cathedral,” we shall find that the architecture and the construction cannot be disjoined. The work of the mediæeval builder in his capacity of artist was to expound, emphasize, and refine upon the work he did in his capacity of constructor, and to develop and heighten its inherent effect. And it is of this kind of skill that the work of the modern engineer, in so far as he is only an engineer, shows no trace.
Reduced to its simplest expression, and as it has actually been used for unknown periods in Asia and in South America, a suspension-bridge consists of two parallel ropes swung from side to side of a ravine, and carrying the platform over which the passenger walks. As the span increases, so that the dip makes the ropes impracticable, the land ends of the ropes are hoisted some distance above the roadway which they carry. If nothing can be found there strong enough to hold them, they are simply passed over, say, forked trees, and the ends made fast to other trees or held down with stones. This is the essential construction of the Brooklyn Bridge. The ropes become four cables sixteen inches thick, of 5541 steel wires; the forked tree becomes a tower 276 feet high, and 8260 square feet in area at the base; the bowlder to hold down the end of the rope becomes a mass of masonry of 60,000 tons’ weight; the shaky platform becomes a great street, 85 feet wide, of five firm roadways. But the man who first carried his rope over the forked tree was the inventor of the arrangement which, developed through all the refinements of modern mechanics, forms the groundwork of the Brooklyn Bridge.
This statement of the germinal idea of a chain-bridge will, perhaps, give a clearer notion of the functions of the several parts of the Brooklyn Bridge than a consideration of the complicated structure in its ultimate evolution, in which these functions are partly lost sight of. But if the structure had been architecturally designed, these things would have been emphasized at every point and in every way. The function of the great “towers,” so called, being merely to hold up the cables, it is plain that three isolated piers would have performed that
BRIDGE AT MINNEAPOLIS.
Thomas M. Griffith, Engineer.
function, and the stability of these piers, loaded as they are by the cables, would very possibly have been assured, even if they had been completely detached from each other. But in order at once to stiffen and to load them, so as to make the area of resistance to the force of the wind equal to the whole area of the towers, the openings through which the roadways run are closed above by steep pointed arches, and the spandrels of these filled with a wall which rises to the summit of the piers, where a flat coping covers the whole. There is a woful lack of expression in this arrangement. The piers should assert themselves starkly and unmistakably as the bones of the structure, and the wall above the arches be subordinated to a mere filling. It should be distinctly withdrawn from the face of the piers instead of being, as in fact it is, only distinguished from them by their shallow and ineffectual projections. It should be distinctly dropped below their summits instead of rising to the same height, and being included under a common cornice. To see what a difference in effect this very obvious differentiation of parts would have made, glance at the sketch of a suspension-bridge at Minneapolis. This is not, upon the whole, a laudable design, and it contains several survivals of conventional architectural forms meaningless in their present place. But the mere subduing of the archway to a strut between the piers explains—not forcibly, perhaps, nor elegantly, but unmistakably—the main purpose of the structure, and the functional relation of its parts. A drawing of one of the towers of the Brooklyn Bridge without its cables would tell the spectator nothing; the structure itself will tell our New-Zealander nothing of its uses. With its flat top and its level coping, indicating that the whole was meant to be evenly loaded, it would seem to be the base of a missing superstructure rather than what it is.
The flatness of the top alone conceals instead of expressing the structure. It is of the first practical necessity that the great cables should move freely in their saddles, so as always to keep the pressure upon the piers directly vertical, and very ingenious appliances have been employed to attain this end, and to avoid chafing the cables. But the design of the piers themselves