loftier nave was built, it, of course, became necessary to heighten the western of the four arches supporting the tower, and afterwards to go through the same process with regard to the eastern arch. At such a time, when the choir was completed, the two arches east and west would be much loftier than the two north and south. Before rebuilding the tower it would naturally occur to the builders to raise the north and south arches to a level with the others, and to do this it would be necessary to raise the roof. In such a case it would be quite natural for the builders to hit upon such a roof as at present exists. They would have before them already the example of a wooden vault in the nave, and for the sake of uniformity they would be inclined to make their new roof as much like that vault as possible. Having the size and height of their arch settled before they designed their roof, the roof would of necessity be shaped to fit the arch, and this would be the most convenient roof for the purpose under the circumstances. This theory will explain why a new roof was required in the fifteenth century, and it also helps to explain other difficulties. For example, it is hard to understand why the transepts, being so wide, are not loftier, and why their original design made a vault impossible. But if we remember that they were originally additions to a much lower nave and choir, we shall see that their architect, having determined on a plan of great width, was in a difficulty. If he made his transepts much higher than his nave, the effect, both inside and out, would be very irregular. If he made them of the same height, and vaulted them, they would be far too wide for their height. He therefore determined, we will suppose, to make a wooden roof which would sacrifice as little of the height of his transepts as possible, and yet allow them to fit on to his nave without any appearance of incongruity. He may also have expected that a loftier nave would soon be built, and set a temporary roof on his transepts which could be easily removed and adapted to new requirements. Be that as it may, the transepts are altogether a curious patchwork, yet when entered from the south end they seem almost entirely satisfactory, since the eye is so engrossed by the magnificence of the five great lancets of the north front, and the great height of the lantern, that it is unable to take note of any smaller and less satisfactory details. The two transepts are alike in the arrangement of their bays and in the general lines of their design, though they differ wholly in the arrangement of their fronts, and in many little points of detail.