Recent experience has shown that the provisions in our existing laws which relate to the sale and transfer of American vessels while abroad are extremely defective. Advantage has been taken of these defects to give to vessels wholly belonging to foreigners and navigating the ocean an apparent American ownership. This character has been so well simulated as to afford them comparative security in prosecuting the slave trade--a traffic emphatically denounced in our statutes, regarded with abhorrence by our citizens, and of which the effectual suppression is nowhere more sincerely desired than in the United States. These circumstances make it proper to recommend to your early attention a careful revision of these laws, so that without impeding the freedom and facilities of our navigation or impairing an important branch of our industry connected with it the integrity and honor of our flag may be carefully preserved. Information derived from our consul at Havana showing the necessity of this was communicated to a committee of the Senate near the close of the last session, but too late, as it appeared, to be acted upon. It will be brought to your notice by the proper Department, with additional communications from other sources. The latest accounts from the exploring expedition represent it as proceeding successfully in its objects and promising results no less useful to trade and navigation than to science. The extent of post-roads covered by mail service on the 1st of July last was about 133,999 miles and the rate of annual transportation upon them 34,496,878 miles. The number of post-offices on that day was 12,780 and on the 30th ultimo 13,028. The revenue of the Post-Office Department for the year ending with the 30th of June last was $4,476,638, exhibiting an increase over the preceding year of $241,560. The engagements and liabilities of the Department for the same period are $4,624,117. The excess of liabilities over the revenue for the last two years has been met out of the surplus which had previously accumulated. The cash on hand on the 30th ultimo was about $206,701.95 and the current income of the Department varies very little from the rate of current expenditures. Most of the service suspended last year has been restored, and most of the new routes established by the act of 7th July, 1838, have been set in operation, at an annual cost of $136,963. Notwithstanding the pecuniary difficulties of the country, the revenue of the Department appears to be increasing, and unless it shall be seriously checked by the recent suspension of payment by so many of the banks it will be able not only to maintain the present mail service, but in a short time to extend it. It is gratifying to witness the promptitude and fidelity with which the agents of this Department in general perform their public duties.