Chap. XXXI.

PRINCIPLES OF PROPORTION.

1611

Fig. 3017.

Windows of Six Divisions are far more complicated, and, though exhibiting greater skillin geometry, are set out precisely upon the same principle. The two equilateral trianglesinclosed within the great circle mark out the prominent features of the design, and theirterminations are the centres of asmany spherical triangles, which,by their crossing, constitute theelaborate filling in.

In some examples, abovethe two main lower divisionsis a circle divided by severalothers, the twelve which areindicated in the figure serving toproportion the tracery of thiscompartment.

At the latter end of the four-teenth century, these designswere so multiplied that almostevery cathedral and church hadits peculiar windows; in Amienscathedral , the chapels constructedat this same time receive theirlight from windows, the heads ofwhich are filled in with traceryexceedingly varied, but thegeneral principles of setting outthe work are preserved; thecircle and the equilateraltriangle were subdividedalmost to infinity, and at noperiod of the arts do-the inventive facul-ties appear so fertile asin that we are nowconsidering. Thegreat west window of '

York Cathedral is thefinest example of theimprovement made inthis mode of deco-ration ; the geometricforms are there so con-cealed by the blendingof the several curves,as to produce con-tinued flowing lines,which is partly shownin fig. 3014. : they are,however, all set outin the same manner,and the centres uponwhich they are struckare established bythe crossing of equi-lateral triangles.

During the epis- 1copacy of John Gran-disson, from the year1327 to 1369, ExeterCathedral was under-going an entire changein its architecture.

Fig. 3018.

To this bishop we are indebted for the great west window, of nine days, and several smallerof four and five, in which are introduced tracery showing a great variety of design; someare composed of equilateral triangles, each containing a trefoil, some of circles with sixturns, others have four and three; but the heads of all, varied as they are, belong to thesame school as fig. 3017.

The great east window at Bristol Cathedral is another fine example of nine days,