When on further inquiry we find that earthworks of this type are exceedingly common in France, and are generally found in connection with feudal castles,[11] and when we consider the area of their distribution in the United Kingdom, and see that they are to be found in every county in England, as well as in Wales and in the Normanised parts of Ireland and Scotland, we see that the Norman invader is the one to whom they seem to point. We see also that small forts of this kind, easily and cheaply constructed, and defensible by a small number of men, exactly correspond to the needs of the Norman invader, both during the period of the Conquest and for a long time after his first settlement here. But it will at once occur to an objector that there have been other invaders of Britain before the Normans, and it may be asked why these earthworks were not equally suited to the needs of the Saxon or the Danish conquerors, and why they may not with equal reason be attributed to them. To answer this question we will try to discover what kind of fortifications actually were constructed by the Saxons and Danes, and to this inquiry we will address ourselves in the succeeding chapters. It will clear the ground greatly if it is recognised at the outset that these earthworks are _castles_, in the usual sense of the word; that is, the private fortified residences of great landowners. It was the chief merit of Mr G. T. Clark's work on _Mediæval Military Architecture_, that he showed the perfect correspondence in plan of these earthen and timber structures with the stone castles which immediately succeeded them, so that it was only necessary to add a stone tower and stone walls to these works to convert them into a Norman castle of the popularly accepted type. We regard the military character of these works as so fully established that we have not thought it necessary to discuss the theory that they were temples, which was suggested by some of our older writers, nor even the more modern idea that they were moot-hills, which has been defended with considerable learning by Mr G. L. Gomme.[12] Dr Christison remarks in his valuable work on Scottish fortifications that an overweening importance has been attached to moot-hills, without historical evidence.[13] And Mr George Neilson, in his essay on "The Motes in Norman Scotland"[14] (to which we shall often have occasion to refer hereafter), shows that moot-hill in Scotland means nothing but mote-hill, the hill of the mote or _motte_; but that _moots_ or courts were held there, just because it had formerly been the site of a castle, and consequently a seat of jurisdiction.[15]