Let us first notice that the Empress grants "feodum et servicium XX militum," while Stephen grants "LX milites feudatos ... scilicet servicium" of so and so "pro [LX] militibus." Thus, then, the "milites feudatos" of Stephen equates the "feodum et servicium ... militum" of the Empress. And, further, it repeats the remarkable expression employed by Florence of Worcester when he tells us that the Conqueror instructed the Domesday Commissioners to ascertain "quot milites feudatos" his tenants-in-chief possessed, that is to say, how many knights they had enfeoffed. But the Empress in her charter complicates her grant by adding the special clause: "Et servicium istorum XX militum faciet mihi separatim preter aliud servicium alterius feodi sui." Had it not been for this clause, one might have inferred that the object of the grant was to transfer, to Earl Geoffrey the "servicium" of these twenty knights' fees due, of right, to the Crown, so that he might enjoy all such profits as the Crown would have derived from that "servicium," and, at the same time, have employed these knights as substitutes for those which he was bound to furnish, from his own fief, to the Crown. But the above clause is fatal to such a view. Again, both in the charters of the Empress and of her rival, these special grants of knights and their "servicium" are kept entirely distinct from those of Crown demesne or escheated land, which, moreover, are expressed in terms of the "librata terræ." On the whole I lean strongly to the belief that, although the working of the arrangement may be obscure, the object of Geoffrey was to add to the number of the knights who followed his standard, and thus to increase his power as a noble and the weight that he could throw into the scale. And the special clause referred to above would imply that the Crown was to have a claim on him for twenty knights more than those whom he was bound to furnish from his own fief. Lastly, we may note the identity of the formula employed for the grant of lands and for that of knights' service. In each case the grant is made "pro tanto,"[338] and in each case the Empress undertakes to make good ("perficere") the balance to him within the limit of the three counties of Essex, Cambridgeshire, and Herts.[339] With the subject of castles I propose to deal later on. But there is one point on which the evidence of this charter is perhaps more important than on any other, and that is in the retrospective light which it throws on the system of reform introduced by the first Henry.