About this period, he made a journey to Virginia, on some business connected with land titles, where he had much intercourse with Major-General Henry Lee; and, on his return, he saw President Washington, at Philadelphia, and was greatly struck by the urbanity and dignity of his manner.  He heard Fisher Ames make his celebrated speech upon the British treaty.  All that the world has said with regard to the extraordinary effect produced by that speech, and its wonderful excellence, is fully confirmed by the opinion of Mr. Mason.  He speaks of it as one of the highest exhibitions of popular oratory that he had ever witnessed; popular, not in any low sense, but popular as being addressed to a popular body, and high in all the qualities of sound reasoning and enlightened eloquence.

Mr. Mason was inclined to exercise his abilities in a larger sphere.  He had at this time made the acquaintance of Aaron Burr and Alexander Hamilton.  The former advised Mr. Mason to remove himself to New York.  His own preference was for Boston; but he thought, that, filled as it then was by distinguished professional ability, it was too crowded to allow him a place.  That was a mistake.  On the contrary, the bar of this city, with the utmost liberality and generosity of feeling and sentiment, have always been ready to receive, with open arms, every honorable acquisition to the dignity and usefulness of the profession, from other States.  Mr. Mason, however, removed to Portsmouth in the autumn of 1797; and, as was to be expected, his practice soon became extensive.  He was appointed Attorney-General in 1802.  About that time, the late learned and lamented Chief Justice Smith retired from his professional duties, to take his place as a judge; and Mr. Mason became the acknowledged head of his profession.  He resigned the office of Attorney-General, three or four years afterwards, to the great regret of the court, the bar, and the country.  As a prosecuting officer, he was courteous, inflexible, and just; careful that the guilty should not escape, and that the honest should be protected.  He was impartial, almost judicial, in the administration of his great office.  He had no morbid eagerness for conviction; and never permitted, as sometimes occurs, an unworthy wrangling between the official power prosecuting, and the zeal of the other party defending.  His official course produced exactly the ends it was designed to do.  The honest felt safe; but there was a trembling and fear in the evil disposed, that the transgressed law would be vindicated.

Very much confined to his profession, he never sought office or political elevation.  Yet he held decided opinions upon all political questions, and cultivated acquaintance with all the leading subjects of the day; and no man was more keenly alive than he to whatever occurred, at home or abroad, involving the great interests of the civilized world.