Chap. XXXI.
PRINCIPLES OF PROPORTION.
1615
The Rose Window in the South Transept at Amiens , 29 feet 6 inches in diameter, is set outupon two squares, which cross each other diagonally.
Fig. 3024.
Sixteen divisions are employed in this figure, and by crossing as many squares, we arriveat the method by which it is set out; each side of the square is equal to the radius bywhich the master line on the outer bead or circle is struck: where the squares cross eachother are the divisions of the pattern, and their several points are the centres upon whichthe pointed arches are struck, which surround the outer portion of the rose.
Where the lines of the squares cross, in the interior of the figure, the smaller divisionsare established, and their points of intersection serve for centres to strike the lesser curves;to show this clearly the whole must be set out, and drawn to a large scale.
The architecture of France underwent a material change after the thirteenth century;the heads of the windows were no longer filled with tracery composed of six foils, generallythree in each window, but branched out into a more running pattern, as practised inseveral parts of England. The fourteenth century not only exhibits windows of moredifficult design, but an apparent absence of the principles by which the several parts wereproportioned to each other. Before the Perpendicular style appeared, great progress hadbeen made in the groining of the spacious vaults of the naves, as well as those of the sideaisles. After the fan tracery was substituted in England, the windows had straightxnullions ascending till they intersected the arch; and we have no further display of thevaried figures that everywhere prevailed before: geometry was now exercised upon theintricacies which their surprising vaults exhibited. It is somewhat singular that we neverfind the beauties of a previous era retained, and blended with that which succeeded.
For the 300 years during which the Pointed style continued to flourish, each half centurygave to it a new character ; hence we have seldom any difficulty in establishing its date :all these changes resulted from an improved knowledge in the art of construction. Thelodges of freemasons were gradually approaching the principles which directed the effortsof the architects of the Byzantine school, and which were found too refined and delicate tobe practised out of Italy after the eleventh century.