Mr. Letcher, the American Minister, left for the United States, on the 26th, and reached New Orleans Feb. 4th. It was supposed that he brought the Tehuantepec treaty ratified with him. A revolt against the central government has occurred in Guanajuato, but it was soon put down by the troops. A number of the ringleaders in it have been executed. The Mexican Government has granted to a company styled Rubio, Barron, Garay, Torre & Co., the whole of the public lands in the State of Sonora, comprising one of the most valuable tracts in the whole country. The Yucatan papers complain loudly of the encroachments of the English in fortifying Belize, and in otherwise interfering in the affairs of the Peninsula. The American Hydrographic Party was busily engaged in surveying the route across the Isthmus. CENTRAL AMERICA. From NICARAGUA we have intelligence to the 13th of January. A rich placer of gold is said to have been discovered about eight miles from Realejo. The crops throughout the country have been seriously threatened by immense flocks of locusts. In consequence of the alarm created by this menaced destruction, the Government has thrown open all the ports of the country to the free admission of all kinds of grain. Don Jose Sacasa has been elected Director of Nicaragua--the term of the present incumbent expiring on the 1st of May. The difficulties between the Government of San Salvador and the British Charge, Mr. Frederick Chatfield, have led to the blockade by the latter, on behalf of his Government, of all the ports of San Salvador. Mr. Chatfield resorted to this extreme measure because the Government refused to comply with his demands, that they should countermand certain instructions they had given to their agents, and contradict, officially, certain statements concerning the British Government made in the public prints of San Salvador. The cause of this blockade was certainly somewhat singular; but the form of it was still more so; for by its terms, British vessels were excluded from its operation. Mr. Chatfield has also written a letter to the Minister for Foreign Affairs of Nicaragua, complaining of the unwillingness of that Government to negotiate with Great Britain, acting on behalf of the King of Mosquito, for a boundary between the territories of Mosquito and those of Nicaragua; and saying that, "as a proof of the conciliatory spirit of the British Government," it had determined to prescribe and maintain a certain boundary line, which is designated. He adds that the British government is still willing to treat on the subject, and urges the importance of "coming to a friendly understanding with the Mosquito government, since _no canal_, or any other improved mode of transit across the Isthmus, can well be established before the difficulty, raised by Nicaragua on this point, is put an end to." In a subsequent letter, enforcing the necessity of arranging the claims of a British house for damages, Mr. Chatfield makes