Several diplomatic appointments have recently been made. Hon. Richard H. Bayard, who was appointed Charge d'Affaires to Belgium, has departed for his mission. Hon. Robert C. Schenck, of Ohio, has been appointed Minister to Brazil, and Hon. J. S. Pendleton, of Virginia, Charge d'Affaires to New Grenada. The Chevalier Gomez, Special Envoy to Rome from the states of Guatemala and San Salvador, has arrived at Washington, and assumed, provisionally, the office of Charge from those states. He has addressed a letter to the Secretary of State in relation to the present condition of the Central American States. General Mosquera, ex-President of New Grenada, is now travelling in this country, and was lately in Washington, where he received distinguished attentions. General Paez, the distinguished exile from Venezuela, is also in Washington. Dr. Frank Taylor, of Pennsylvania, who has recently returned from Constantinople and Asia Minor, has received letters from the illustrious Kossuth, addressed to the Secretary of State, and soliciting the intervention of the United States with the Turkish Government, to procure the release of himself and his compatriots, and their transportation to the United States. Mr. Webster immediately complied with the request, and has dispatched instructions to Mr. Marsh, the American Minister at Constantinople, to procure from the Turkish Government the release of the Hungarians. The frigate St. Lawrence has sailed from New-York for Southampton, with articles for the World's Fair. She carries out between four and five hundred articles, embracing nearly all branches of manufacture, and the principal mineral and agricultural productions of the country. The contributions are in charge of Charles F. Stansbury, Esq., agent of the Central Committee of Washington. The tender of the authorities of Southampton, offering the use of that port, with free transportation of the goods to Vauxhall, London, has been accepted by the Secretary of State. There have been several serious wrecks, with loss of life, on the Atlantic coast and the Mississippi river. The steamboat America, which left Wilmington, N.C., on the fourteenth of January, for Mobile, foundered on the 29th. The schooner Champion, of Boston, picked up one boat's crew, containing six men. A second boat, containing ten men, was picked up by the schooner Star, and taken to Washington. A third boat, containing six men, has not been heard from. The steamer John Adams, on her way from New Orleans to Cincinnati, struck on a snag in the Mississippi river, on the morning of January 27th. The cabin parted from the hull, which went down in sixty feet water. Out of 230 cabin and deck passengers, firemen, and crew, 123 were lost, of whom 82 were German and Irish emigrants, and returning Californians. On the ninth of February, the steamer Autocrat, from New Orleans to Memphis, came in contact with the steamer Magnolia, coming down the river, and sank instantly. Thirty lives were lost.