4. We see, towards the end of the period, from the way in which the Norman arches were used to intersect each other, and form two pointed arches within a round-headed arch, that a change in style was showing itself. Towards the end of Norman times, in the reigns of Richard I and John, we reach what architects call the =Transition Period=, when the Norman style was gradually changing into the =Early English=, or Pointed Style. The choir of Canterbury Cathedral is one of the best-known specimens of this Transition Period. Just as changes took place in the style of the buildings, so, too, the life of the nation changed. All the changes were not improvements; some, indeed, were changes for the worse. [Illustration: Photo. Valentine CHOIR OF CANTERBURY CATHEDRAL (page 70)] =Summary.=--The Norman period lasted for 130 years, from 1066 to about the year 1200. The round-headed style of building, called Norman, lasted through this period. It became more ornamented as the years went on. In the latter part of the time the style began to change. St. Alban's Cathedral and Durham Cathedral have examples of plain and highly ornamental Norman work. The choir of Canterbury Cathedral gives an example of Transition work at the end of Norman days. CHAPTER XIX CASTLES 1. The passion for building castles in England had begun before the Norman Conquest; but during the Norman period a great many castles (about 1100, it is said) were built in various parts of the country. They were not all of the same size, strength, or importance. Some were royal castles, belonging to the king, who placed each one in charge of a constable or warden. These were necessary for the defence of the country. We should expect to find important castles, for instance, at such places as Carlisle, Ludlow, Gloucester, Dover, and London. We can, too, trace lines of castles along the Scottish and Welsh borders; and there were no fewer than twenty-five in the county of Monmouth alone. 2. Many castles were placed on the site of Saxon strongholds, and of strongholds dating from still earlier times. Others were built where the overlord thought they would be of service to him in protecting his interests and keeping his tenants in order. So it often came to pass that the castles were built close to, or in the very heart of, a town or city. Frequently the castle was at once the protection and the terror of the neighbourhood. [Illustration: Norman Castle.--From a drawing in Grose's Military Antiquities.--1, The Donjon-keep. 2, Chapel. 3, Stables. 4, Inner Ballium. 5, Outer Ballium. 6, Barbican. 7, Mount, supposed to be the court-hill, or tribunal, and also the place where justice was executed. 8, Soldiers' Lodgings.]