developments of the piers on the ground-story level—developments which constitute one of the most interesting branches of the subject, and afford important illustration of some of the fundamental principles of the Gothic style.
In the transitional buildings with sexpartite vaults the main piers, made up of square members and engaged vaulting shafts, like those of Senlis and Noyon, could hardly be improved as regards their functional adjustment and expression. But they were so massive as to take up a great deal of room, and hence were more or less inconvenient. It was probably to avoid this inconvenience that plain round columns were employed for the ground-stories in Paris and Laon; but these round columns were soon felt to be unsatisfactory, as affording no independent supports for the various members of the superstructure. Such columns did not partake of the new principles that now characterised every other constructive member of the building. Attempts to improve them were therefore made, and a new and strictly functional form was soon devised, a very early, perhaps the first, example of which may be studied in the nave of the Cathedral of Paris.
FIG. 26.The first step in the change appears to have been connected with a new adjustment to its load of the form of the abacus of the great capital of the round column,—an adjustment rendered necessary by the employment of two arch orders in the great arcade instead of one. In the choir of Paris the arches of the great arcade are of one order on the choir side, and of two orders on the side of the aisle, as in the plan (Fig. 26). The transverse rib, a, of the aisle vault is so wide that the diagonals, b and c, which are also rather wide, leave little of the abacus surface unoccupied on the aisle side; and the bases of the vaulting shafts, d, e, f, on the
