dry
ditch and flattened at the top. Around the crest of its summit was
placed a timber palisade. This moated mound was styled in French _motte_
(latinized _mota_), a word still common in French place-names. It is
clearly depicted at the time of the Conquest in the Bayeux tapestry, and
was then familiar on the mainland of western Europe. A description of
this earlier castle is given in the life of John, bishop of Terouanne
(_Acta Sanctorum_, quoted by G.T. Clark, _Medieval Mil.
Architecture_):--"The rich and the noble of that region being much given
to feuds and bloodshed, fortify themselves ... and by these strongholds
subdue their equals and oppress their inferiors. They heap up a mound as
high as they are able, and dig round it as broad a ditch as they can....
Round the summit of the mound they construct a palisade of timber to act
as a wall.... Inside the palisade they erect a house, or rather a
citadel, which looks down on the whole neighbourhood." St John, bishop
of Terouanne, died in 1130, and this castle of Merchem, built by "a lord
of the town many years before" may be taken as typical of the practice
of the 11th century. But in addition to the mound, the citadel of the
fortress, there was usually appended to it a bailey or basecourt (and
sometimes two) of semilunar or horseshoe shape, so that the mound stood
_a cheval_ on the line of the enceinte. The rapidity and ease with which
it was possible to construct castles of this type made them
characteristic of the Conquest period in England and of the Anglo-Norman
settlements in Wales, Ireland and the Scottish lowlands. In later days a
stone wall replaced the timber palisade and produced what is known as
the shell-keep, the type met with in the extant castles of Berkeley,
Alnwick and Windsor.

[Illustration: Section From Clark's _Medieval Military Architecture_, by
permission of Bernard Quaritch.

FIG. 1.--Plan of Laughton en-le-Morthen.]

But the Normans introduced also two other types of castle. The one was
adopted where they found a natural rock stronghold which only needed
adaptation, as at Clifford, Ludlow, the Peak and Exeter, to produce a
citadel; the other was a type wholly distinct, the high rectangular
tower of masonry, of which the Tower of London is the best-known
example, though that of Colchester was probably constructed in the 11th
century also. But the latter type belongs rather to the more settled
conditions of the 12th century when haste was n