CURVILINEAR PERIOD. _Lady Chapel_, _Choir_, _Central Tower_.—But a much more important work remained, which had hitherto been postponed, owing perhaps to the great expense involved in the completion of the west front and the chapter-house. It was to extend the choir eastwards. Many of the great cathedrals had finished their eastward extensions long before. Canterbury choir had been prolonged at the beginning of the twelfth century, and again about 1180. Hereford also was lengthened about 1180. The Angel Choir of Lincoln had been built about 1280. But at Wells, Lichfield and Chester, the extension of the choir was not effected till the Curvilinear period (1315-1360). As at Lichfield, the Wells architect seems first to have built the Lady chapel as a detached building, afterwards joining it up to the Transitional bays of Fitz-Jocelyn’s choir. As every one knows, it is the most beautiful east end we have in England. It may be worth while to try to see how this design was arrived at—a design as exceptional as it is effective. The simplest form of east end in English Gothic is seen at York and Lincoln: it consists merely of a low wall with a big window above it. The next improvement is to build an aisle or processional path behind the east end; at the same time piercing the east wall with one, two, or three arches. This was done at Hereford about 1180; and on a magnificent scale in the Chapels of Nine Altars at Durham and Fountains early in the thirteenth century. But the French apsidal cathedrals—of which we have an example in Westminster—have not only an encircling processional aisle, but also a chevet of chapels radiating out from it; thus providing ever-changing vistas of entrancing beauty. The next step in England also was to provide our rectangular choirs with a chevet as well as with a processional aisle. An early example of this plan is to be seen at Abbey Dore, in Herefordshire, about 1190. It occurs early in the thirteenth century, on a still grander scale, at Salisbury; where one finds not one, but two processional aisles, as well as chapels to the east of them; and, in addition, a Lady chapel projecting still farther to the east, thus producing a design of great complexity and beauty. Nevertheless, at Salisbury, since the chief supporting piers of the retro-choir and the chevet are in a line with those of the choir, there is by no means the same changeful intricacy of vista that affords one ever fresh delight in an apsidal church. At Wells, however, the architect attained all the success of the Continental builder, simply because he built his Lady chapel not rectangular but octagonal. For, to get this octagon, of which only five sides were supported by walls, he had to plant in the retro-choir two piers to support the remaining three sides; and these piers are necessarily out of line with the piers of the choir. He had got the Continental vista. He saw it; but he saw also that it could be improved upon.