It is obvious that so small a number of instances furnishes a very slender basis for generalisations as to the characteristics of early Norman keeps, if we ask in what respect they differed from those of the 12th century. But it is the object of this chapter to suggest research, rather than to lay down conclusions. The four early instances mentioned should be compared with the earliest keeps of France, the country where the pattern was developed. This has not yet been done in any serious way, nor does the present writer pretend to the knowledge which would be necessary for such a comparison.[1112] But data exist, which, if they were used in the right way, would greatly add to our knowledge. In the first place, we have a list of the castles built by Fulk Nerra, Count of Anjou, at the end of the 10th and the beginning of the 11th century, during his life-long struggle with the Counts of Blois for the possession of Touraine. This list may be regarded as authentic, as it is given by his grandson, Fulk Rechin, in the remarkable historical fragment which he has bequeathed to us.[1113] The list is as follows:--_In Touraine_: Langeais, Chaumont-sur-Loire, Montrésor, St Maure. _In Poitou_: Mirabeau (N.W. of Poitiers), Montcontour, Faye-la-Vineuse, Musterolum (Montreuil-Bonnin), Passavent, Maulevrier. _In Anjou_: Baugé, Chateau-Gontier, Durtal. "Et multa alia," adds Fulk's grandson. Nine of these others are mentioned by the chroniclers: Montbazon, Semblançay, Montboyau, St Florent-le-Vieil, Chateaufort near Langeais, Chérament, Montrevault, Montfaucon, and Mateflon. Many of these were undoubtedly wooden castles, with wooden keeps on mottes.[1114] In many other cases the ancient fabric has been replaced by a building of the Renaissance period. Whether any remains of stone donjons built by Fulk Nerra exist at any of these places except at Langeais, the writer has been unable to find out; probably Langeais is the only one; but French archæologists are agreed that the ruined tower which stands on the ridge above the 15th-century castle of Langeais is the work of this count,[1115] a venerable fragment of a 10th-century keep.[1116]