He arrived at Berlin shortly after his marriage, in the autumn of 1797. In 1798 he received an additional commission to negotiate a treaty of commerce with Sweden. While residing at Berlin, with a view to perfecting himself in the German language, he made a translation into English of Wieland's " Oberon," and would have published it but for the appearance about that time of a translation by Sotheby. In 1800 he travelled through Silesia, of which tour he wrote an account in a series of letters to his brother which were published, though without the writer's knowledge, in the "Port Folio," a weekly paper at Philadelphia. These letters were collected and published in a volume in London, and, being translated into French and German, had a wide circulation. On the accession of Mr. Jefferson to the presidency, John Q. Adams was recalled; but he had previously succeeded in negotiating a treaty of commerce with Prussia. Returning to Boston, he again opened a law office there. In 1802 he was elected from Suffolk county (which includes Boston) to the Massachusetts senate, and the next year was chosen by the legislature a senator in congress from Massachusetts. He owed this position to the federal party of Massachusetts, and for four years he continued to sustain their views; but on the question of the embargo recommended by Jefferson he separated from them.

The Massachusetts election in the preceding spring had resulted in the success of the Jeffersonian party, who elected their candidates for governor and lieutenant governor, and a majority in both branches of the legislature. At the time when the embargo was proposed by the president to congress, it seemed probable that the question of Adams's reelection to the senate would have to be decided by a legislature favorable to the views of the national administration; and the support which Adams gave to that measure was charged by the federalists to the hope of securing his reelection and the favor of a party whose predominance seemed at length established, not merely in the nation, but in Massachusetts also. This course on his part led to a warm controversy between him and his colleague in the senate, Timothy Pickering, who now made the same charges of treacherous selfishness against the son which he had formerly brought against the father. Pickering addressed a letter to Governor Sullivan of Massachusetts, in which he forcibly stated his objections to the embargo, which he represented as the first step toward a war with Great Britain, a step into which the administration had been led, as he maintained, by French threats or French seduction.

This letter Pickering requested the governor to lay before the legislature, which Sullivan refused to do, on the ground that it was " seditious and disorganizing." It found its way, however, into the newspapers, and Adams replied to it through the same medium. In this reply he expressed his conviction that the whole of the difficulties in which the United States were involved on the question of neutral rights, including the issue of Bonaparte's Berlin and Milan decrees, had originated in the unwarrantable maritime pretensions of Great Britain. He even went so far as to represent the late British orders in council, issued nominally in retaliation for the Berlin decree, as a first step on the part of Great Britain toward bringing back the United States to colonial subjection. Giving emphatic expression to suspicions and to an antipathy which, as to the Hamiltonian or Essex junto section of the federalists, he had imbibed from his father, he broadly hinted that Pickering and his special party friends were quite ready to side with Great Britain in the new enterprise which he ascribed to her of re-subjecting America. Although Sullivan had been reelected governor, the embargo had operated to give the federalists a small majority in both branches of the Massachusetts legislature; and when the question of the choice of senator came up, Adams was dropped, and Lloyd, a Boston merchant, chosen in his place.

Adams thereupon declined to sit for the remaining short session of his term, resigned his sena-torship, and retired to private life. He had previously, however, secured, in addition to his practice as a lawyer, a new resource and employment, in the post of professor of rhetoric and belles-lettres at Harvard college. He entered upon this professorship in 1806, upon condition of not being obliged to reside at Cambridge, and for three years following discharged the duties of it, delivering lectures, the first, it is said, ever read in any American college, and conducting exercises in declamation. His lectures, which were printed in 1810, once possessed a considerable reputation, but are now entirely neglected. The winter subsequent to his resignation he visited Washington, nominally for the purpose of attending the supreme court. During this visit he sought and obtained a confidential interview with Jefferson, in which he distinctly brought against a portion of the federal leaders the charge of a treasonable design of dissolving the Union and forming a separate northern confederacy.

The same charge, thus privately made, he not long after repeated in print, in a review of the writings of Fisher Ames, which he published in numbers in the "Boston Patriot." Such was the origin of a charge which for the next ten or fifteen years strongly affected the administration of the government, and which, penetrating deeply into the popular mind, made the leading statesmen of New England objects at once of dread and hatred, deprived New England for a considerable period of its natural weight in public affairs, and had a decisive influence in curtailing to a single term the presidential office, to which John Q. Adams himself afterward attained. That he was sincere in bringing this charge there is little room for doubt. The proof, however, which he presented at the time or afterward of the truth of this plot, was sufficiently slender. It was said to have originated with a few federal members of congress,' in consequence of the annexation of Louisiana - a measure which Adams had himself opposed, being one of the six senators who voted against it - and the threatened destruction, by the addition of so much new western and southern territory, of the political influence of the northern and eastern states.