In the cathedral at Chartres we have examples of the two extremes of these transitional windows. In the windows of the aisles of the nave (Woodcut No. 650) the circle is small and insignificant, and only serves to join together the two lancets. In the clerestory (Woodcut No. 651), which is somewhat later, the circle is all important and quite overpowers the lower part. Here it is in fact a circular window, supported by a rectilinear substructure. In both these instances the discharging arch still retains its circular form, and the tracery is still imperfect, inasmuch as all the openings are only holes of various forms cut into a flat surface, whereas to make it perfect, it is necessary that the lines of two contiguous openings should blend together, being separated by a straight or curved moulded mullion, and not merely pierced as they are in this instance. This may perhaps be better illustrated by one of the windows of the side-aisles at Rheims, where the pointed Gothic window has become complete in all its essential parts. Even here it will be observed how awkwardly the circle fits into the spherical triangle of the upper part of the window. Indeed, there is an insuperable awkwardness in the small triangles necessarily left in fitting circles into the spaces above the lancets, and beneath the pointed head of the openings. When four or five lights were used instead of two, this defect became more apparent; and even in the example from St. Ouen (Woodcut No. 653). one of the most beautiful in France, the architect has not been able to obviate the discordance between the conflicting lines of the circle and spherical triangle. At last, after two centuries of earnest trial, the builders of those days found themselves constrained to abandon entirely these beautiful constructive geometric forms, for tracery of a more manageable nature, and in place of the circle they invented first a flowing tracery, of which the window at Chartres (Woodcut No. 654) is an exquisite example; and then having shaken off the trammels of constructive form, launched at once into all the vagaries of the flamboyant style. In this style stone tracery was made to look bent and twisted, as willow wands. Its forms, it must be confessed, were always graceful, but constructively weak, and frequently extravagant, showing a complete contrast to the contemporary perpendicular style followed in England. That failed from the stiffness of its forms; this from the fantastic pliancy with which so rigid a material as stone was used. Greatness or grandeur was as impossible in flamboyant tracery, as grace and beauty were with the perpendicular style; still for domestic edifices, and for the smaller churches erected in the 16th century, it must be confessed the flamboyant style has a charm it is impossible to resist. It is so graceful and so fantastically brilliant, that it captivates in spite of our soberer reason, lending as