ative than those of a mechanical nature. And it will be found on examination that the requirements of the eye are admirably felt and skilfully met in these arch mouldings.
The characteristic forms were developed early, and little material change was made during the period through which
FIG. 132.
the style continued in its integrity. The square transverse arches of Romanesque vaults, like those of Poissy (a, Fig. 132), were heavy in appearance, and were little improved by the chamfer that was sometimes given them, as in the profile b, in the same figure, from Morienval. In the apsidal aisle of St. Martin des Champs at Paris some interesting examples occur, in which the sections differ one from another, as at c, d, and e. These are apparently so many experiments made
FIG. 133.
with the object of lightening the effect of these heavy ribs and of producing profiles which should be more varied and agreeable to the eye. In the transverse ribs of St. Denis a vast improvement was made, and one of the most characteristic Gothic profiles was fully established. The section a,
