But the abstract, hypothetical, and variable portions of the craft--or, if you will, of the science--depending on ten thousand varying and variable circumstances--depending on persons, passions, fancies, whims; caprices royal, national, parliamentary, and personal, is above theory, and beyond the reach of books; and can only be learned by experience, by practice, and by the most perfect and intuitive tact. The traditional political maxims, the character of the loading sovereigns, statesmen, and public men in any given court, as well as the conduct of negotiations, may be acquired by study, by observation, by a residence as secretary, as _attache_; but who, unless a man of real genius for his art--who, unless a man of real ability and talent, shall seize on, fix, and turn to his purpose, the ever-mobile, the ever-varying phases of courts, of camps, of councils, of senators, of parliaments, and of public bodies? No doubt there are certain great cardinal and leading principles with which the mind of every aspirant should be stored. But the mere knowledge of principles, and of the history of the science can never alone make a great embassador, any more than the reading of treatises on the art of war can make a great commander. An embassador at a first-rate court should, indeed, be the minister of foreign affairs for his country on a small scale; and we know well enough that the duties devolving on a minister for foreign affairs are grave, are delicate, are all important. The functions appertaining to the ministry for foreign affairs have been in England during the last two years, and certainly also were from 1793 to 1815, the most important and the most difficult connected with the public administration. A man to fill such a post properly, requires not merely elevation and uprightness of character, but experience, tried discretion, the highest capacity, the most extensive and varied knowledge and accomplishments. Yet how few embassadors (we can scarcely name one) have been in our day, or, indeed, for the last century, elevated into Principal Secretaries of State for Foreign Affairs! Such promotions in France have been matters of every-day occurrence since and previous to 1792. Dumouriez, Talleyrand, Reinhard, Champagny, Maret, Bignon, Montmorency, Chauteaubriand, Polignac, Sebastiani, De Broglie, Guizot, Soult, had all been embassadors before they were elevated into the higher, the more responsible, and the more onerous office. In England, since the accession of George I., we can scarcely cite, speaking off-hand, above four instances.