If we compare the position and powers of the ealdorman with those of the duke on the continent, we shall find several points of difference which deserve notice. In the imperial constitution of the German states, as it was modified and settled by Charlemagne, the duke was a superior officer to the comes, count or graf, and a duchy for the most part comprehended several counties, over which the duke exercised an immediate jurisdiction[307]. Occasionally no doubt there were counties without duchies, and duchies without counties, that is where the duke and count were the same person: sometimes the dukes were hereditary dynasts, representing sovereign families which had become subject to the empire of the Franks, and who continued to govern as imperial officers the populations which either by conquest or alliance had become incorporated with it; such were the dukes in Bavaria and Swabia. In other cases they were generals, exercising supreme military power over extensive districts committed to their charge, and mediately entrusted with the defence and government of the Markgraviats or border-counties which were established for the security of the frontiers. The variable, and very frequently exceptional, position of these nobles or ministerials, while it renders it difficult to give an accurate description of their powers which shall be applicable to all cases, often accounts for the events by which we are led to recognize modern kingdoms in the ancient duchies, and to trace the derived and mediate authority down to its establishment as independent royalty. ----- Footnote 307: I refer generally here to the doctrines of Eichhorn, Staats- und Rechtsgesch. i. 460. etc.; and to the works of the great German authors who have treated this subject and others connected with it, more especially to Dönniges, Deutsches Staatsrecht, p. 96 _seq._ -----