ment of two arches in the buttress system became practically constant; and perhaps the grandest illustration of the type is that which is afforded in the nave of Amiens (Fig. 44). In double-aisled buildings a double system of flying buttresses was introduced, one system over each aisle. In these cases the dividing piers of the aisles rise through the aisle roof, above which they receive the heads of the outer system of arches and give foothold to the inner one. The flying buttresses of the apse of Reims (Fig. 45) are of this form.
FIG. 45.
The evolution and adjustment of the pinnacle, which is so conspicuous a feature in this last example, was rapid after the device of weighting the top of the buttress had been introduced. At Chartres, where the superincumbent weight terminates in a truncated oblong pyramid in place of the
