To those in search of new light on our early mediaeval history, I commend the first portion of this work, as setting forth, for their careful consideration, views as evolutionary on the Domesday hide and the whole system of land assessment as on the actual introduction of the feudal system into England. Although I have here brought into conjunction my discovery that the assessment of knight-service was based on a five-knights unit, irrespective of area or value, and my theory that the original assessment of land was based on a five-hides unit, not calculated on area or value, yet the two, one need hardly add, are, of course, unconnected. The one was an Anglo-Saxon system, and, as I maintain, of early date; the other was of Norman introduction, and of independent origin. My theories were formed at different times, as the result of wholly separate investigations. That of the five-hides unit was arrived at several years ago, but was kept back in the hope that I might light on some really satisfactory explanation of the phenomena presented. The solution I now propound can only be deemed tentative. I would hope, however, that the theories I advance may stimulate others to approach the subject, and, above all, that they may indicate to local students, in the future, the lines on which they should work and the absolute need of their assistance. Perhaps the most important conclusion to which my researches point is that Domesday reveals the existence of two separate systems in England, co-extensive with two nationalities, the original _five hides_ of the 'Anglo-Saxon' in the south, and the later _six carucates_ of the 'Danish' invaders in the north.[3] No one, I may add, is better qualified to carry further these inquiries than Prof Maitland, whose brilliant pen has illumined for us the origins of English law. Himself engaged on the study of Domesday, he kindly offered to withhold his conclusions until my work should have appeared.[4] Among the fresh points here discussed in connection with Domesday Book will be found the composition of the juries by whom the returns were made, the origin and true character of the _Inquisitio Eliensis_, and the marked difference of the two volumes compiled from the Domesday returns. Of the six early surveys dealt with in conjunction with Domesday, I would call attention to that of Leicestershire as having, it would seem, till now remained absolutely unknown. It has long been a wish of mine to deal with these surveys,[5] not only as belonging to a period for which we have no records, but also as illustrating Domesday Book. In 'The Knights of Peterborough' will be found some facts relating to Hereward 'the Wake', which seem to have eluded Mr Freeman's investigations, and even those of Mr Tout.