As we have seen in a previous chapter, tracery originated from the necessity of piercing that portion of the wall which was left vacant when two lights were gathered under a single arched dripstone, and therefore elementary tracery consisted merely of apertures in a flat surface. As the possibilities of this ornamental feature became better understood, the mullions were recessed from the face of the wall and the fine effect thus produced was, as the art progressed, much enhanced by the introduction of various orders of mullions, and by recessing certain portions of the tracery from the face of the mullions and their corresponding bars. The geometrical tracery, as we have seen, consists of various combinations of the circle, as the trefoil, based on the triangle, the quatrefoil on the square, the cinquefoil on the pentagon, etc. [Illustration: A Late Decorated Window in a Parish Church. East Sutton, Kent. _Photograph Gardner Waterman._] In Curvilinear windows the tracery, although based on the same forms and figures, is yet so blended into an intricate pattern that each figure does not stand out with the same individuality as in the Geometric. Among our most beautiful Geometric windows are those of the Lady Chapel at Exeter, Ely Chapel, and Merton Chapel, Oxford, and of the Curvilinear our best example is probably the east window of Carlisle Cathedral. It must be noted that beautiful as are Curvilinear windows, yet they mark a certain decadence in Gothic architecture, in that it is an irrational treatment of stone, and conveys the idea that the material was bent and not cut into the required shape, it being a well-established canon in art that when strength is sacrificed to mere elegance it marks a decline in that art. [Side note: Decorated Capitals and Piers.] Decorated capitals as a rule follow the contour of the pier in clustered columns, and are either bell-shaped or octagonal. They are frequently only moulded, thus presenting rounds, ogees and hollows, on which the prevailing ornaments of the period, the ball and the square flower, are set. The foliated sculpture is most exquisite, and is gracefully wreathed around the bell, instead of rising from the astrigal or upper member of the capital, as in the earlier style. [Illustration: Examples of Decorated Ornament. Finial Capital Finial (Wimborne Minster). (York Minster). (York Minster). Square Flower. Ball Flower. Crocket Cornice Crockets (Hereford Cathedral). (Grantham). (York Minster). _Drawn by E. M. Heath._]