From the diplomatic papers contained in the sixth volume of the present edition of Mr. Webster's works it appears that the first step taken by Mr. Webster, after receiving the directions of the President in reference to the negotiation, was to invite the coöperation of Massachusetts and Maine, the territory in dispute being the property of the two States, and under the jurisdiction of the latter. The extent of the treaty-making power of the United States, in a matter of such delicacy as the cession of territory claimed by a State to be within its limits, belongs to the more difficult class of constitutional doctrines. We have just seen both the theory and practice of General Jackson on this point. The administration of Mr. Tyler took for granted that the full consent of Massachusetts and Maine was necessary to any adjustment of this great dispute on the principle of mutual cession and equivalents, or any other principle than that of the ascertainment of the true, original line of boundary by agreement, mutual commission, or arbitration. Communications were accordingly addressed to the governors of the two States. Massachusetts had anticipated the necessity of the measure, and made provision for the appointment of commissioners. The legislature of Maine was promptly convened for the same purpose by the late Governor Fairfield. Four parties were thus in presence at Washington for the management of the negotiation: the United States and Great Britain, Massachusetts and Maine. Recollecting that the question to be settled was one which had defied all the arts of diplomacy for half a century, it seemed to a distant, and especially a European observer, as if the last experiment, exceeding every former step in its necessary complication, was destined to a failure proportionably signal and ignominious. The course pursued by the American Secretary, in making the result of the negotiation relative to the boundary contingent upon the approval of the State commissioners, was regarded in Europe as decidedly ominous of its failure.