If this treaty shall receive the approbation of the Senate, it will terminate a difference respecting boundary which has long subsisted between the two Governments, has been the subject of several ineffectual attempts at settlement, and has sometimes led to great irritation, not without danger of disturbing the existing peace. Both the United States and the States more immediately concerned have entertained no doubt of the validity of the American title to all the territory which has been in dispute, but that title was controverted and the Government of the United States had agreed to make the dispute a subject of arbitration. One arbitration had been actually had, but had failed to settle the controversy, and it was found at the commencement of last year that a correspondence had been in progress between the two Governments for a joint commission, with an ultimate reference to an umpire or arbitrator with authority to make a final decision. That correspondence, however, had been retarded by various occurrences, and had come to no definite result when the special mission of Lord Ashburton was announced. This movement on the part of England afforded in the judgment of the Executive a favorable opportunity for making an attempt to settle this long-existing controversy by some agreement or treaty without further reference to arbitration. It seemed entirely proper that if this purpose were entertained consultation should be had with the authorities of the States of Maine and Massachusetts. Letters, therefore, of which copies are herewith communicated, were addressed to the governors of those States, suggesting that commissioners should be appointed by each of them, respectively, to repair to this city and confer with the authorities of this Government on a line by agreement or compromise, with its equivalents and compensations. This suggestion was met by both States in a spirit of candor and patriotism and promptly complied with. Four commissioners on the part of Maine and three on the part of Massachusetts, all persons of distinction and high character, were duly appointed and commissioned and lost no time in presenting themselves at the seat of the Government of the United States. These commissioners have been in correspondence with this Government during the period of the discussions; have enjoyed its confidence and freest communications; have aided the general object with their counsel and advice, and in the end have unanimously signified their assent to the line proposed in the treaty. Ordinarily it would be no easy task to reconcile and bring together such a variety of interests in a matter in itself difficult and perplexed, but the efforts of the Government in attempting to accomplish this desirable object have been seconded and sustained by a spirit of accommodation and conciliation on the part of the States concerned, to which much of the success of these efforts is to be ascribed.