those customarily used places the designer in the need of a new standard of æsthetics. In developing such a standard, the fundamental criterion of fitness will be that of attaining the highest functional efficiency and employing it in the appearance of the entire construction. When this is attained, the old standards will gradually be made to conform to the new conditions.

In suggesting that "if a steel trussed bridge, economically and wisely constructed according to our present light, offends our ideals of grace and beauty, the fault perhaps is not in the structure, but in the rigidity and immobility of the ideals which have been established by conditions long since outgrown in the progress of science," Mr. Van Brunt has probably indicated the lines of convergence of engineering practice and architectural ideals; for while, as before stated, much can be done with most bridge designs to improve them without increasing their cost or affecting their efficiency, on the other hand, it is often impossible for an engineer to modify a bridge design so as to meet fully the critical objections of a good architect without introducing features both faulty and expensive. However, it must not be inferred from the foregoing that the author is defending the many bridge designers in their indifference to the artistic in construction. He believes that the preceding letter of Mr. Van Brunt's gives a very just and unprejudiced statement of the status of affairs at the time of its writing. But of later years more attention has been given to æsthetics in bridge design; and the author feels that some progress in artistic bridge construction has been made.

In 1897 the author wrote thus in De Pontibus:

"The principal hindrance to the progress of æsthetic reform in bridge-building is liable to emanate from the bridge-manufacturing companies, who have been so accustomed to submitting competitive designs, and who have made in the past so much money thereby, that they will naturally consider any fundamental innovation of this kind as detrimental to their interests. Nevertheless, when some concerted action on the part of bridge specialists is inaugurated with the object of making bridge structures more sightly, it is probable that the manufacturing companies will be far-sighted enough to recognize that their true interests will not be subserved by offering any serious opposition to the proposed reform. Some obstruction is likely to come from managers of railroads, who have for years been used to buying their bridges as cheaply as possible without any regard to appearance, and too often with very little in respect to constructive excellence. It will devolve upon the chief engineers and the bridge engineers of railroads to influence the managements of their lines so as to incline them towards a more favorable consideration for appearance when deciding upon the designing and purchasing of their bridges.

"But the moulders of public opinion in respect to the necessity for a due consideration of architectural effect in bridge-building must, of necessity, be the independent bridge engineers of the country, who are not so much influenced by monetary motives as are engineers connected with railways and bridge companies, although it must be confessed that some of the most prominent bridge specialists are the greatest offenders against the principles of æsthetics.

"There is a general impression among engineers that to ingraft architectural effects upon bridge construction will always involve the necessity for an increased expenditure

of money; but this notion is incorrect, because there are many large and important bridges in the United States which could have been beautified, and at the same time cheapened, without in the slightest degree impairing their strength, rigidity, or efficiency, by simply modifying their harsh and uncompromising lines. It requires the expenditure of more thought than money to obtain an artistically designed bridge; for a little money will go a long way in producing a decorative effect upon such a structure.

"The author is a firm believer in the principle that true economy, engineering excellence of construction, and the best architectural effect will almost invariably be found to accompany each other, and be inseparable in the designing of any bridge. Moreover, any bridge built with due consideration for, first, efficiency, second, appearance, and, third, economy, will be satisfactory and gratifying to not only the trained expert, but also to the general engineer and railroad man, and even to the public; because when an observer notes that in such a structure all the engineering requirements are properly provided for, that there is no evident waste of material, and that all due advantage has been taken of the conditions to render the bridge sightly and in harmony with its surroundings, his eye will of necessity be pleased, and his inherent sense of fitness will cause him to regard the structure with a feeling of pleasure.

"To recognize and acknowledge the deficiencies of modern bridge designs from the artistic point of view is one thing, but to show how they are to be remedied is another; because, while it is easy to say that a certain structure does not come up to one's ideal of grace and beauty, it is very difficult to show exactly where the defects are, and what should or could be done to remove them."

Notwithstanding this, the author believes that the fundamental precepts previously enumerated, if followed consistently, will eliminate the most glaring sources of ugliness in bridge designs. To secure positive and satisfactory results in the decorative architectural details is more. difficult, as that is a matter requiring special training; and, therefore, it cannot well be done through mere instinct.

In making a study of the æsthetics of a bridge design, after determining what spans are applicable, it is well to make one or more layouts on a large scale on the brown paper that is used in engineers' offices for pencildrawings, indicating the circumscribing lines of all main members to scale, and tinting or filling between the said lines with pencil-shading; then tack the paper on a wall, and stand off at various distances to judge the effect. By doing this one can form a very correct opinion concerning the comparative merits of several layouts, and can ascertain where and how any particular layout can be improved. A consultation with several members of one's office force upon the architectural features of the various designs will often result in an improved effect; for nothing else will bring out both the favorable and the unfavorable characteristics of a plan like discussion. In the outlining of each span a great deal can be accomplished toward beautifying a structure, and there is no better way to study the general effect of any proposed outline than the one just indicated, viz., laying out various trusses to scale, tacking the paper to a wall, and criticising them. It will surprise any one who tries this method to see how quickly he can detect the slightest variation from correctness in outline, and what a difference in effect even a small change

in a truss depth will produce. It was in this way that the trusses of the author's bridge over the Missouri River at East Omaha were proportioned; and it is doubtful if any improvement could be effected in their outlines when all the factors involved in the question are duly considered, for Mr. Van Brunt gave his unqualified approval of the architectural effect of these outlines. In this problem there were but three points to determine, viz., the depths of truss at the two hips and the depth at the tower, for the number of panels was settled by economic considerations, and the

straightness and section of the top chords were necessitated by certain questions of efficiency. The depth at the outer hips was first determined by the requirements for clearance, rigidity, and appearance, then the depths at the intermediate hips and tower were settled by trial and discussion from the artistic point of view, due attention being paid to the engineering questions involved by the various inclinations of top chords and inclined inner posts. In Fig. 52k is reproduced a photograph of the long swing spans of that structure.

Fig. 521 shows an outline diagram of an alternative design for the movable span of the Pacific Highway Bridge at Portland, Ore., which is being engineered by the author's firm. In the bidding competition between this span and a vertical lift the latter was adopted on account of its superior economy and more satisfactory operation. The outlines of the swing span are good, although the author is of the opinion that those of the East Omaha swing are better.

By no stretch of the imagination can any bascule bridge be termed a thing of beauty. On the contrary, most of them are glaringly ugly, as can be seen by examining the various illustrations of Chapter XXX.

The lack of symmetry in a single-leaf bascule militates greatly against its appearance, and no addition of tower entrance or filigree construction can help it. The intrusion of an immense mass of concrete into the scenery is far from being artistic, and in most cases the counterweight has to be above the level of the deck. There is a condition, though, where the bascule construction can be adopted without much, or perhaps any, detriment to the aesthetics; but even in that case it cannot be said to add to the appearance, its effect being neutral rather than either posi

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•484-0"

FIG. 521. Layout of the Swing Span in the Alternative Design for the Pacific Highway Bridge over the Columbia River at Portland, Ore.

tive or negative. The condition is that of a fairly low, highway, deck structure where the required clear opening is comparatively small. By using a double-leaf bascule with the bottom chords arched, keeping the counterweight entirely below the deck, and making all the fixed spans arches of about the same span length and general appearance as in the bascule, a good effect can be produced. In Fig. 52m is a layout of this type, being a study submitted a few years ago by the author to the City Engineer of Vancouver, B. C., for a proposed bridge over False Creek at Thurlow street. The bridge has not yet been built, but some day there will be a structure at or near that location, for the regular development of the city will necessitate one.

Nor is it an easy matter to fit a vertical lift span into a structure and obtain a fine architectural appearance; but the very magnitude and massiveness of the construction generally produce a pleasing effect upon the mind of the beholder, as do also the simplicity and the evident efficiency of the method of operation. A study of the illustrations in Chapter XXXI will convince one of the correctness of this assertion, and will prove to him that there is nothing inherently ugly in the vertical lift bridge as there is certainly in the bascule.

In determining the outlines of a span these few elementary principles are to be borne in mind:

First. There is nothing so ugly in a bridge as parallel chords unless it be a skew. However, for spans between one hundred and twentyfive feet and two hundred feet it is often best to use them, although in

certain cases where the loads are great it is practicable to adopt polygonal top chords for spans considerably shorter than the superior limit just mentioned.

Second. While it is generally economical of material to use very long panels, no such extreme length should be adopted as would involve an awkward appearance due to flatness of diagonals.

Third. The curvature of the top chord should be made as great as is consistent with a proper consideration of web stiffness and counterbracing.

Fourth. When it is practicable in Petit trusses to curve the top chord to such an extent as to make too small the inclination of the endposts to the horizontal, it is permissible to let the latter extend over one panel only and to make all the main diagonals extend over two panels. The effect is ungraceful, however, when the main diagonals occupy one panel each near the ends of the span, and two panels each elsewhere.

Fifth. When appearance alone is in question, trusses very deep at mid-span are desirable; but an excessive truss depth is conducive to a reversion of bottom-chord stress by the wind load-a condition which has either to be avoided or provided for by stiffening the bottom chords. In extremely heavy bridges, especially where the dead load is unusually great, it is possible that an undue consideration for economy of metal might cause a designer to adopt a truss depth which would be actually too great for appearance, but this is not likely to occur very often because of other limiting conditions.

Sixth. There are certain limiting relations between width of bridge, depth of truss, and length of span which, for the sake of good effect, ought not to be exceeded. Usually the rules established on account of purely engineering questions will prevent these limits from being transgressed, thus proving a maxim which the author has often maintained, viz., that in any design any violation of engineering principles is also a violation of good taste from an artistic point of view.

Seventh. A very graceful effect can be obtained by placing the lower horizontal struts of the overhead bracing in a cylindrical surface similar to that which contains the panel points of the top chords, but, of course, with different curvature.

In respect to the decoration of each span of a bridge, it may be stated that a little ornamentation is generally much better than a great deal, and that this little should be appropriate and in keeping with the general character of the structure. A prodigal use of cheap cast-iron trimmings at a portal of a steel bridge is not in good taste, but it is perfectly proper to decorate the intersections of the members of the portal bracing by plates or rosettes, to surmount the upper horizontal portal strut by an æsthetically designed parapet, to use ornamental corner brackets beneath the lower portal strut, to employ fancy name-plates symmetrically arranged, and to place ornamental figures of proper size and design at the