Immediately after entering the Abbey Church by the north door, it will be well, in order to get a general idea of its size and beauty, to take one's stand close to the west wall under the large lancet window. There is nothing to break the view from the west to the east walls of choir and ambulatory, a total distance of about 250 feet; for the wooden screen which separates the choir from the crossing is too light and open to break the vista. It will be noticed that with the exception of the western bays of the nave, and the three-light geometrical windows in the eastern wall of the choir, and the two windows of the ambulatory, everything is Norman or transitional in character. The aisles have stone quadripartite vaulting except in the added bays to the west, where the vaulting is merely plaster. The high roof, like many in Norman churches, is a wooden one, for Norman builders rarely dared to throw a stone vault over the nave or choir, for as yet the principle that allows such a piece of engineering to be carried out with safety, namely, the balancing of thrust and counter-thrust, by means of vaulting ribs and external flying buttresses, had not been fully realized in England. In some few cases it is true that late Norman vaults may be found, but more often where stone vaults exist in Norman churches they were added in after times. In Romsey Abbey one of the most noteworthy features is that very little alteration was made in the church when once it was built. True there was a westward extension in the thirteenth century, and some insertion of windows in the fourteenth century, but nothing of the original church seems to have been swept away, as was so often the case, to make room for extensions and alterations. The #Nave# has seven bays, to the east of which is the transept, and beyond it the choir, which has three bays. Further to the east, as we shall find in due course, may be seen the low vaulted retro-choir or ambulatory of one bay. [Illustration: CYLINDRICAL PIER: NORTH NAVE ARCADE] It is well known that Norman choirs were generally short, and that when we find a considerable length of building eastward of the crossing, this eastward extension was made in the thirteenth or fourteenth century; the new building being often begun to the east of the Norman choir, and the choir left untouched until the eastern part was finished, when very frequently the old Norman choir and presbytery were demolished, and the new work joined on to the transept by masonry in the later style.