The amount of business which devolved on him during his mission to Berlin, independent of the negotiations for a commercial treaty with the German Customs-Union or Zollverein, can hardly be estimated by reading his dispatches only. Not a week elapsed without his receiving letters from different parts of Germany and the United States, asking for advice with regard to emigration, or to the disposition of property left by friends in America or in Germany, and all requiring immediate attention. But notwithstanding these demands upon his time, he did not neglect the pursuits of literature. In 1838 he published, jointly with Dr. Crichton, the volumes entitled "Scandinavia," which form a portion of the Edinburgh Family Library; and in 1842, and the succeeding years, wrote a number of interesting letters addressed to the National Institute at Washington, which were published in the columns of the National Intelligencer. In 1844, he was named Member of the Academy of Sciences at Berlin, and we must not omit to mention, that he was the only foreign diplomat to whom the honor had then been awarded. With Raumer and Ranke, with Ritter, the celebrated geographer, Encke, the astronomer, he was of course acquainted; Savigny, Gans, and Eichorn, he knew well; and with Alexander von Humboldt he was on the most friendly and familiar terms. Count Raczynski, whose work on "Modern Art," has made his name known in this country, and whose fine gallery is to amateurs of painting one of the chief objects of interest in Berlin, was also his intimate friend. With Bunsen, one of the most agreeable as well as intellectual men in Germany, whose diplomatic duties kept him absent from Berlin, he passed many delightful hours in Switzerland, and in London. All his colleagues in Berlin met him on the most friendly terms; but the Russian, French and English ministers were those whose company he most enjoyed, and who perhaps entertained for him the most cordial friendship. The two latter gave him their entire confidence, often showing him their dispatches, and freely discussing with him the interests of their respective governments. It was in the spring of 1844, that the negotiations with the Zollverein, with which Mr. Wheaton had been charged, and which the various interests of the nineteen different states which it then included, had protracted, drew to a close. On the 25th of March he signed a convention with Baron Bulow, the Prussian Minister of Foreign Affairs, of whose enlightened and liberal views he always spoke in high terms. This treaty, to the accomplishment of which he had devoted all his energies during several years, and which he fondly hoped would prove satisfactory to Government and the country, was rejected by the Senate. It is hardly necessary to say, that he felt this disappointment deeply.