addition of an acute gable above the top arcade between the towers. [1]
The west fronts of Senlis, Paris, Amiens, and Reims sufficiently illustrate the development and the characteristics of the French-Gothic façade. Its typical form, as exhibited in the Cathedral of Amiens, is truly a marvel of architectural design. With the given elements and conditions it is hard to see how a more consistent and beautiful product could have been created. The arch, the shaft, the buttress, and the dividing string are employed in it not only with mechanical propriety, but with the most subtle artistic feeling. Indeed, by the simple adjustment of proportions the Gothic builders, in these structures, wrought wonders.
Nor ought we to convey the impression that structural developments were altogether wanting in this part of the building, though it is true that here such developments were fewer, and were hardly ever apparent externally.
M. Viollet-le-Duc has shown, [2] for instance, that in vast buttresses like those of the façade of Paris the tendency to settlement of the mortar beds is greater at the inner part, which is the more heavily weighted, than at the outer face. This inequality of settlement would tend to cause rupture were the buttress constructed of mere horizontal beds of masonry all of the same material. But if the weight falling on the lower portions of the inner part were diminished by a system of props carried up obliquely at different levels from the outer face, the tendency to rupture would be neutralised. Accordingly it has been found that the buttresses of the façade of Paris have an internal structure consisting of a superposed series of inclined masses of harder masonry which conduct a great part of the weight from the inner portion to the outer face of the buttress. To secure the outer face against yielding to the outward push of these props the bonding of the masonry is reinforced, at the levels where they find foothold, by cramps of iron. The buttress thus becomes really an organic structure, exhibiting something of the dynamic principle which reigns throughout the rest of the building.
