Of King’s Langley Priory, which is known to have been in existence in 1400, a considerable portion still exists. Ashridge House now occupies the site of a large monastery and college, of which there are many remains. A brief reference may here be made to St Albans’ clock-tower, which was erected between 1403 and 1412, and from which the curfew was rung till so late as 1861, while a bell was also rung early in the morning to awaken work-people. [Illustration: The Priory, King’s Langley] 17. Architecture. (_b_) Military--Castles. Like most other counties in the south of England, Hertfordshire possesses the remains of several Norman castles, most of which appear to date back no further than the Conquest, while others, like Berkhampstead (where, as we have seen in a previous section, Mercian kings held their courts), have been supposed to be constructed on the site of earlier buildings of a similar nature. The total number of castles built by the Normans to overawe their new English subjects is stated to have been about 1100. These, as may naturally be surmised, varied considerably in size, some being royal castles, constructed for the defence of the country generally and ruled by a constable or guardian, while others belonged to individual Norman noblemen for the defence of their own estates, and were for the most part the terror of the surrounding districts. A Norman castle of the highest type occupied a large area, the lofty and massive outer wall enclosing a space of several acres, and being surmounted with towers and protected by bastions, while it was also surrounded by a moat or ditch. Within the enclosure thus formed were three main divisions, the first of which was the outer bailey, or courtyard, entered by a towered gateway furnished with a portcullis (that is to say, a gate which could be dropped down from, and drawn up into, the tower by means of a system of chains and pulleys) and a drawbridge. The stables and other buildings were contained in this court. Next came the inner bailey, or quadrangle, likewise entered through a towered and fortified gateway, and containing the chapel, the barracks, and the keep. Lastly, we have the keep or donjon itself, which always contained a well, and constituted the final portion which was defended during a protracted siege when the garrison was hard pressed. In choosing the site for such a military castle, either a more or less isolated and steep hill or rock might be selected, or a situation in marshy low-lands, where access might be rendered difficult or impossible by damming back the waters.