April 3rd.—I had an interview with the Southern Commissioners to-day, at their hotel.  For more than an hour I heard, from men of position and of different sections in the South, expressions which satisfied me the Union could never be restored, if they truly represented the feelings and opinions of their fellow-citizens.  They have the idea they are ministers of a foreign power treating with Yankeedom, and their indignation is moved by the refusal of Government to negotiate with them, armed as they are with full authority to arrange all questions arising out of an amicable separation—such as the adjustment of Federal claims for property, forts, stores, public works, debts, land purchases, and the like.  One of the Judges of the Supreme Court of the United States, Mr. Campbell, is their intermediary, and of course it is not known what hopes Mr. Seward has held out to him; but there is some imputation of Punic faith against the Government on account of recent acts, and there is no doubt the Commissioners hear, as I do, that there are preparations at the Navy Yard and at New York to relieve Sumter, at any rate, with provisions, and that Pickens has actually been reinforced by sea.  In the evening I dined at the British Legation, and went over to the house of the Russian Minister, M. de Stoeckl, in the evening.  The diplomatic body in Washington constitute a small and very agreeable society of their own, in which few Americans mingle except at the receptions and large evening assemblies.  As the people now in power are novi homines, the wives and daughters of ministers and attaches are deprived of their friends who belonged to the old society in Washington, and who have either gone off to Secession, or sympathise so deeply with the Southern States that it is scarcely becoming to hold very intimate relations with them in the face of Government.  From the house of M. de Stoeckl I went to a party at the residence of M. Tassara, the Spanish Minister, where there was a crowd of diplomats, young and old.  Diplomatists seldom or never talk politics, and so Pickens and Sumter were unheard of; but it is stated nevertheless that Virginia is on the eve of secession, and will certainly go if the President attempts to use force in relieving and strengthening the Federal forts.