Optical Refinements in Architecture.
Many architects look upon all refinements of line and curve as so much waste time, and would as soon think of referring to the original Latin of Vitruvius for rules in proportioning their rooms as to consult and apply the corrections of the Parthenon to their buildings. In sketching out his design to a small scale on a sheet of Whatman’s drawing paper, the architect does so without any further thought than to produce a convenient plan or a well grouped elevation. Any infinitesimal correction to the straight line or entasis would be inappreciable to the naked eye on the surface of paper the inequalities of which would render it worthless; nor does he take much trouble in the proportions of his rooms, so long as they look right and fit well. If such refinements are to be made, they should be shown in large drawings, or set out to the full size on the works by proper rules and other instruments. The task is laborious and troublesome, and contract prices are little in sympathy with such niceties of adjustment. Even of the more practicable mode of adopting certain ratios and proportions, the architect does not avail himself very much.
We do not say that every horizontal beam—such as an entablature supported by columns at intervals—ought to be “corrected” by the application of a parabolic curve, or that every string course and cornice should be arranged to curve or bend upward; but we contend that these refinements ought to be made in interiors wherever the lines are long, and contrasting lines and surfaces occur in juxtaposition; that they are, in truth, applying precisely the same principle of correction as the colorist or decorator would apply when he takes care to juxtapose two colors or shades which shall be complementary to or harmonize with each other.
It is painful to witness in modern buildings a perfect ignoring of these principles of design. We go into a public hall or concert room, and take our seat. The flat coffered ceiling appears to be literally bending or falling upon our heads. To make the impression still more apparent, the architect has introduced a circular or flatly curved arch over the orchestral recess. If the ceiling is a flat curve, as it often is, the trusses are, perhaps, brought down below and incased, their lower edges being made perfectly horizontal, the two lines serving to increase the difference between them; in other words, to make the trusses look as if they were deflecting.
Mr. Pennethorne, some years ago, showed that the masses of the temples of Athens and Rome were designed on perspective principles—that is to say, the masses and many of the details were designed as they were intended to be viewed. The point of sight was always before the architect—that is to say, he studied the effect of his entablatures, abaci, and other masses of details from points of view that were likely to be frequented. It is well known that the various sections through the Doric capitals, the mouldings, and other parts of Athenian buildings, were composed of different arcs of the conic sections. Mr. Pennethorne says that the Greek entablature is perspectively proportioned and arranged to suit the given points of sight thus: The apparent height of entablature is measured in seconds upon the arc of a great circle. “Then, dividing this whole apparent height into some given number of aliquot parts, measured also in seconds, the apparent height of the architrave, of the frieze, and cornice will, in each case, be a multiple of this given modulus. Again, by dividing the first modulus into a given number of apparent aliquot parts, a second modulus is obtained, by which the apparent heights of all the details of the cornice of architrave and frieze will be regulated, and the true lineal heights are then all determined by trigonometrical calculations.” In short, all the visible heights of features are, upon this principle, regulated from a given point, the real elevational height of each part being afterward found.
This system of proportion would probably entail too much labor upon the architect to work out with any accuracy, and may be looked upon as chimerical. But we see instances every day of positive ignorance of these principles, especially in the designing of mouldings, projecting features, and towers. If the architect is too impatient to make nice corrections in the manner we have pointed out, he ought at least to take the trouble necessary to regulate his heights and masses before inking in his elevations. Sketching in perspective is a valuable auxiliary in designing roughly the masses of a building; but some more accurate method is required in perspectively setting out the heights of stories, entablatures, parapets, towers, and other features. This can only be done by adjusting all heights from a given point of sight, or upon the arc of a circle described from the said point. An elevation is misleading, as every architect knows who has suffered disappointment after the building is finished. It only gives vertical heights, which may be very much curtailed or foreshortened in the actual view of the building from the opposite side of the street, for example.
Many towers and spires have been spoiled by designing them in elevation instead of at the angle. In broach spires we find a want of care in one particular above the others. The broach is designed on the level. The hips of the broach are made to look gentle in elevation, but when raised above the eye 60 or 100 feet, they become so depressed as to give a very ungraceful and abrupt springing to the spire.
We may instance the want of entasis to spires and columns. Every one who has a critical sense of vision must have observed the apparent weakness there is in a spire that has perfectly straight sides, when compared with one which has been entasised, and the same with all columns. Here also the method to insure the correction can be easily applied. The more important of these refinements are capable of being made at the initial stage of design, without recourse to decimals of two or three removes from the decimal point, or to mathematical calculations.—Abstract from the Building News.