In December, Chateaubriand used in the House of Peers the words which Mr. Gallatin had said to him, 'that England could not take Cuba without making war on the United States, and that she knew it.' Mr. Gallatin so informed Adams, and added, that France would no doubt agree, as Chateaubriand would have agreed, to a tripartite instrument if England were of the same opinion.
In March, 1827, Adams warned Gallatin that the sudden and unexpected determination of Great Britain to break off all negotiation concerning the colonial trade, and the contemporaneous interdiction of the vessels of the United States from all British ports in the West Indies, had put a new face on matters. A renewal of the convention of 1818 would probably be agreed to by the Senate, but no concession in the form of a treaty would be acceptable. His words were emphatic. “One inch of ground yielded on the northwest coast,—one step backward from the claim to the navigation of the St. Lawrence,—one hair's breadth of compromise upon the article of impressment would be certain to meet the reprobation of the Senate.” In this temper of parties, Adams added, "All we can hope to accomplish will be to adjourn controversies which we cannot adjust, and say to Britain as the Abbé Bernis said to Cardinal Fleuri: 'Monseigneur, j'attendrai.'”
But changes now occurred in the British ministry: Lord Liverpool died in February, 1827—Mr. Canning in the following August. Lord Goderich became prime minister. The new administration returned from Canning's eccentric course to the old and quiet path. The commercial convention of 1815 was renewed indefinitely, each party being at liberty to abrogate it at twelve months' notice. The joint occupancy of the Oregon Territory, agreed to in 1818, was continued in a similar manner. On September 29 a convention was signed, referring the northeast boundary to the arbitration of a friendly sovereign. Mr. Gallatin believed that, had Canning lived, he would have opened a negotiation on the subject of impressment. Huskisson considered that 'the right, even if well founded, was one the exercise of which was intolerable, but that this was not the time to take up the subject.' The new British administration did not dare to encounter the clamor of the navy, the opposition of the Tories, and the pride of the nation on this question.
Having accomplished all that was practicable, completed all the current business, and leaving the British government in a better temper than he found it, Mr. Gallatin returned to the United States, reaching New York on November 29, 1827. Nothing remained in foreign relations in respect to which Mr. Gallatin felt that he could be of much use except the northeast boundary. In a letter of congratulation to Mr. Gallatin on his arrival, President Adams made ample amends for all his harsh judgments, expressed or withheld. The three conventions were entirely satisfactory to him. Of the negotiation he said, in words as graceful as warm, “I shall feel most sensibly the loss of your presence at London, and can form no more earnest wish than that your successor may acquire the same influence of reason and good temper which you did exercise, and that it may be applied with as salutary effect to the future discussions between the two governments.” During his visit to London Mr. Gallatin was overwhelmed with civilities. Canning was courteous to a degree, and rarely a day passed that the American ambassador had not to choose between half a dozen invitations to dinner. At the house of the Russian minister, the Count de Lieven, he was always welcome, and the Countess de Lieven, the autocrat of foreign society in London, without whose pass no stranger could cross the sacred threshold of Almack's, was his fast friend. To each circle he carried that which each most prized. Whether the conversation turned upon government or science, the dry figures of finance, or the more genial topic of diplomatic intrigue, Mr. Gallatin was its easy master, and his words never fell on inattentive ears.
With this mission to London Mr. Gallatin's diplomatic service closed. He would have accepted the French mission in 1834, and so informed Van Buren, but General Jackson, who was President, had his own plans, and 'ran his machine' without consulting other than his own prejudices or whims. But although Mr. Gallatin was no longer in the field of diplomacy, his counsels were eagerly sought. The northeastern boundary was a troublesome question, indeed in the new phases of American politics an imminent danger. The extension of the commercial relations of Great Britain and the United States rendered it imperative that no point of dispute should remain which could be determined. For two years after his return from England, Mr. Gallatin was employed in the preparation of an argument to be laid before the king of the Netherlands, who had been selected as the arbiter between the United States and Great Britain on the boundary. The king undertook to press a conventional line, which the United States, not being bound to accept, refused. In 1839 Mr. Gallatin prepared, and put before the world, a statement of the facts in the case. This, revised, together with the speech of Mr. Webster, a copy of the Jay treaty, and eight maps, he published at his own expense in 1840.
At this time conflicts on the Maine frontier brought the subject up in a manner not to be ignored. Popular feeling was at high pitch. In this condition of affairs Alexander Baring, who had been raised to the peerage as Lord Ashburton, was sent to America on a mission of friendship and peace. As a young man he had listened to the debate on Jay's treaty in 1795. He was now to be received by Webster in Washington in the same spirit in which Grenville received Jay in London, when it was mutually understood that they should discuss the matter as friends and not as diplomatists, and leave their articles as records of agreement, not as compromises of discord. Gallatin eagerly awaited the arrival of his old friend, and was grievously disappointed when contrary winds blew the frigate which carried him to Annapolis. Letters were immediately exchanged; Lord Ashburton engaging before he left the country to find Gallatin out, and, as he said, to “draw a little wisdom from the best well.” After the treaty was signed, Lord Ashburton went from Washington to New York, and the old friends met once more: Mr. Gallatin was in his 82d year, but in the full possession of his faculties; Lord Ashburton in his 68th year: a memorable meeting of two great men, whose lives had much in common; the one the foremost banker of England, the other the matchless financier of America; and to this sufficient honor was added for each the singular merit of having negotiated for his country the most important treaty in its relation to the other since the separation of 1783,—Mr. Gallatin, the Treaty of Ghent, which gave peace to America; Lord Ashburton, that treaty which is known by his name and which secured peace to Great Britain.
In 1846 Mr. Gallatin rendered his last diplomatic service by the publication of a pamphlet on the Oregon question, which was then as threatening as that of the northeastern boundary had been. This admirable exposition, which put before the people as well as the negotiators the precise merits of the controversy, powerfully contributed to the ultimate peaceful settlement.
Still once more Mr. Gallatin threw his authoritative words into the scale of justice. His last appearance in public had been when he presided on April 24, 1844, at a meeting in New York city to protest against the annexation of Texas. He then held that the resolution of the House declaring the treaty of annexation between the United States of America and the Republic of Texas to be the fundamental law of union between them, without and against the consent of the Senate, was a direct and undisguised usurpation of power and a violation of the Constitution. In the storm of opposition he lifted his feeble voice in condemnation of the violation of treaties, and the disregard of the sacred obligations of mankind. “I am highly gratified,” were his final words, "I am highly gratified that the last public act of a long life should have been that of bearing testimony against this outrageous attempt. It is indeed a consolation that my almost extinguished voice has been on this occasion raised in defense of liberty, of justice, and of our country." Of the war with Mexico, he was wont to say, “that it was the only blot upon the escutcheon of the United States.” Aged as he was, he would not rest until he had made his last appeal for peace with Mexico. He also prepared supplementary essays on war expenses: the first of these was published in 1847, the second in 1848. For months all his faculties, all his feelings were absorbed in this one subject. These pamphlets were widely circulated by the friends of peace. The venerable sage had the comfort of knowing that his words were not in vain. Peace with Mexico was signed on February 2, 1848.
Mr. Gallatin was no believer in the doctrine of 'manifest destiny,'—the policy of bringing all North America into the occupation of a race speaking the same language, and under a single government. On February 16, 1848, before news of the signature of the treaty at Guadalupe Hidalgo, by Mr. Trist, the American negotiator, was known in New York, Mr. Gallatin condemned this idea in a remarkable passage, in a letter to Garrett Davis:—