The acts of Congress establishing new mail routes and requiring more expensive services on others and the increasing wants of the country have for three years past carried the expenditures something beyond the accruing revenues, the excess having been met until the past year by the surplus which had previously accumulated. That surplus having been exhausted and the anticipated increase in the revenue not having been realized owing to the depression in the commercial business of the country, the finances of the Department exhibit a small deficiency at the close of the last fiscal year. Its resources, however, are ample, and the reduced rates of compensation for the transportation service which may be expected on the future lettings from the general reduction of prices, with the increase of revenue that may reasonably be anticipated from the revival of commercial activity, must soon place the finances of the Department in a prosperous condition. Considering the unfavorable circumstances which have existed during the past year, it is a gratifying result that the revenue has not declined as compared with the preceding year, but, on the contrary, exhibits a small increase, the circumstances referred to having had no other effect than to check the expected income. It will be seen that the Postmaster-General suggests certain improvements in the establishment designed to reduce the weight of the mails, cheapen the transportation, insure greater regularity in the service, and secure a considerable reduction in the rates of letter postage--an object highly desirable. The subject is one of general interest to the community, and is respectfully recommended to your consideration. The suppression of the African slave trade has received the continued attention of the Government. The brig Dolphin and schooner Grampus have been employed during the last season on the coast of Africa for the purpose of preventing such portions of that trade as were said to be prosecuted under the American flag. After cruising off those parts of the coast most usually resorted to by slavers until the commencement of the rainy season, these vessels returned to the United States for supplies, and have since been dispatched on a similar service.