At noon this day we found ourselves once more sailing on the Atlantic, and bade farewell to the Gulf of Florida without having heard any news of the dreaded Commodore Mitchell. The narrow and dangerous part of this Gulf is about two hundred miles in length, and fifty in breadth, bordered on one side by the coast of Florida, and on the other, first by Cuba, and then by the Bahama Islands, of which the Manilla reef forms the extremity, and which reef also terminates the Gulf.