In his address before the Mississippi Democratic Convention, in July, 1859, from which we have already quoted, Mr. Davis said: "We have witnessed the organization of a party seeking the possession of the Government, not for the common good, not for their own particular benefit, but as the means of executing a hostile purpose against a portion of the States." Approaching more directly the doctrine of Mr. Seward, he said: "The success of such a party would indeed produce an 'irrepressible conflict.' To you would be presented the question, Will you allow the Constitutional Union to be changed into the despotism of a majority? Will you become the subjects of a hostile Government? or will you, outside of the Union, assert the equality, the liberty and sovereignty to which you were born? For myself I say, as I said on a former occasion, in the contingency of the election of a President on the platform of Mr. Seward's Rochester speech, let the Union be dissolved. Let the 'great, but not the greatest, evil' come; for, as did the great and good Calhoun, from whom is drawn that expression of value, I love and venerate the Union of these States, but I love liberty and Mississippi more." When Congress assembled, in December, 1859, the lawless expedition of John Brown had greatly accelerated the inevitable climax of disunion. Thenceforward the incipient revolution was, to a great extent, transferred from the hands of Congress, whose action was but lightly regarded in comparison with the animated scenes which marked the State conventions and popular assemblages, held with reference to the approaching presidential nominations. Mr. Davis approved the test made at the Charleston Convention, by the Southern Democracy, as to the construction of the Cincinnati platform, and the demand for a more explicit announcement of the position of the party concerning slavery in the Territories. His speech, in reply to Judge Douglas, on the 16th and 17th of May, 1860, is a vindication of Southern action at Charleston, and an exhaustive discussion of all the phases of the issue upon which the Democracy had divided. Events soon demonstrated the irreconcilable nature of the antagonism which had severed this giant organization. It had simply realized the destiny of political parties. In one generation they rise, as a virtue and a necessity, to remedy disorders and reform abuses; in another generation, they are themselves the apologists of corruption and the perpetrators of wrong. The Democratic party became insensible to the appeals of principle, and its fifty years' lease of power terminated, not speedily to be recovered. HON. JEFFERSON DAVIS AT PORTLAND, MAINE. [From the Eastern Argus.]