RETURN OF MR. DAVIS TO THE SENATE--OPENING EVENTS OF MR. BUCHANAN'S ADMINISTRATION--TRUE INTERPRETATION OF THE LEGISLATION OF 1854-- SENATOR DOUGLAS THE INSTRUMENT OF DISORGANIZATION IN THE DEMOCRATIC PARTY--HIS ANTECEDENTS AND CHARACTER--AN ACCOMPLISHED DEMAGOGUE--DAVIS AND DOUGLAS CONTRASTED--BOTH REPRESENTATIVES OF THEIR RESPECTIVE SECTIONS--DOUGLAS AMBITION--HIS COUP D'ETAT, AND ITS RESULTS--THE KANSAS QUESTION--DOUGLAS' TRIUMPHS OVER THE SOUTH AND THE UNITY OF THE DEMOCRATIC PARTY LOST--"SQUATTER SOVEREIGNTY"--PROPERLY CHARACTERIZED--DAVIS' COURSE IN THE KANSAS STRUGGLE--DEBATE WITH SENATOR FESSENDEN--PEN-AND-INK SKETCH OF MR. DAVIS AT THIS PERIOD-- TRUE SIGNIFICANCE OF POLITICAL EVENTS TO THE SOUTH--SHE RIGHTLY INTERPRETS THEM--MR. DAVIS' COURSE SUBSEQUENT TO THE KANSAS IMBROGLIO--HIS DEBATES WITH DOUGLAS--TWO DIFFERENT SCHOOLS OF PARLIAMENTARY SPEAKING--DAVIS THE LEADER OF THE REGULAR DEMOCRACY IN THE THIRTY-SIXTH CONGRESS--HIS RESOLUTIONS--HIS CONSISTENCY--COURSE AS TO GENERAL LEGISLATION--VISITS THE NORTH--SPEAKS IN PORTLAND, BOSTON, NEW YORK, AND OTHER PLACES--REPLY TO AN INVITATION TO ATTEND THE WEBSTER BIRTH-DAY FESTIVAL--MR. SEWARD'S ANNOUNCEMENT OF THE "IRREPRESSIBLE CONFLICT"--MR. DAVIS BEFORE MISSISSIPPI DEMOCRATIC STATE CONVENTION--PROGRESS OF DISUNION--DISSOLUTION OF THE DEMOCRATIC PARTY--SPEECHES OF MR. DAVIS AT PORTLAND AND IN SENATE. Mr. Davis returned to the Senate at a period marked by agitation, no less menacing to the Union than that which had so seriously threatened it in 1850. His health at this time was exceedingly infirm, and for several months he was so much prostrated by his protracted sufferings, that a proper regard for the suggestions of prudence would have justified his entire abstinence from the labors and excitements of this stormy period. Again and again, however, did his heroic devotion carry him from his sick bed to the capitol, to engage in the death-struggle of the South, with her leagued enemies, for safety in the Union, which she was still loath to abandon, even under the pressure of intolerable wrong. Frequently, with attenuated frame and bandaged eyes, he was to be seen in the Senate, at moments critical in the fierce sectional conflict; and at the final struggle upon the Kansas question, not even the earnest admonitions of his physician, that to leave his chamber would probably be followed by the most dangerous results, were availing to induce his absence from the scene. The opening events of the first session of the Thirty-fifth Congress, (the first incidental to the administration of Mr. Buchanan,) were far from being auspicious of the continued unity of the Democratic party, which, for several years past, the intelligence of the country had correctly appreciated as an essential condition to the preservation of the Union.