The slave-trade has been extensively pursued in the Congo. A British steam-cruiser, for many years, has been stationed off its mouth, making many captures. Under American nationality, however, several vessels have entered, taken in a cargo of slaves and escaped. The natives, near the mouth of the river, have been rendered treacherous and cruel by the slave-trade; but a short distance in the interior, they are represented as being civil and inoffensive, disposed to trade in elephants’-teeth and palm-oil.

After crossing the Congo, the Perry communicated with Kabenda, and the day following anchored at Loango, in company with the British cruiser stationed off that point. The British commodore arriving the next day, a letter was addressed to him, dated April 4th, asking whether any suspected vessels had been seen on the south coast, by the cruisers under his command, since the capture of the Chatsworth, on the 11th of September, 1850; also requesting that he would express his views of the present state of the slave-trade on the southern coast of Africa.

In reply, the British commodore made the following communication:

“I beg to acquaint you that the only report I have received of a suspected vessel, under American colors, having been seen on the south coast since the date you have named, was from H. M. steam-sloop Rattler, of a schooner showing American colors having approached the coast near Old Benguela Head; which vessel, when Commander Cumming landed subsequently, was reported to him, by the people on shore, to have shipped slaves near that place.

“Your inquiry applies only to the south coast; but it will not be irrelevant to the general subject and object for which we are co-operating, if I add that the schooner Bridgeton, of Philadelphia, under the American flag, was visited by Her Majesty’s steam-sloop Prometheus, off Lagos, on the 22d of August, under circumstances causing much suspicion, but with papers which did not warrant her seizure by a British officer; and that I have since received information from Her Britannic Majesty’s consul at Bahia, that the same vessel landed three hundred slaves there in October.

“I also take this opportunity of bringing under your notice another American vessel, which I observed at Sierra Leone under the American flag; and which was reported to me, by the authorities there, as being to all appearance a legal trader, with correct papers, but whose real character and ultimate object I have since had much reason to doubt.

“I inclose a copy of the formal entry of this vessel, ‘The Jasper,’ at the port of Sierra Leone, from which you will observe that her cargo was shipped at the Havana; and that in the manifest are shooks and heads of water-casks, and that she had on board three passengers: these passengers were Spaniards. The Jasper staid a short time at Sierra Leone, disposed of some trifles of her cargo for cash, and left for Monrovia. On proceeding a few days afterwards in the Centaur (the flag-ship) to that place, I found that she had disposed of more of her cargo there, also for cash, and was reported to have proceeded to the leeward coast; and I learned from the best authority, that of the passengers, one was recognized as being a Spanish slave-dealer who had been expelled from Tradetown, in 1849, by President Roberts, and that the others were a Spanish merchant, captain and supercargo; and that the American captain had spoken of his position as being very indefinite.

“On the second subject, my view of the present state of the slave-trade on the south coast: It is formed on my own observations of the line of coast from Cape St. Paul’s to this port, and from the reports which I have received from the captains of the divisions, and the commanders of the cruisers under my orders, as well as from other well-informed persons on whom I can rely, that it has never been in a more depressed state, a state almost amounting to suppression; and that this arises from the active exertions of Her Majesty’s squadron on both sides of the Atlantic, and the cordial co-operation which has been established between the cruisers of Great Britain and the United States on this coast, to carry out the intention of the Washington treaty; and latterly from the new measures of the Brazilian government.

“Factories have been broken up at Lagos, in the Congo, and at Ambriz; although of this I need hardly speak, because your own observation during the past year must satisfy you of the present state of depression there.

“The commencement of last year was marked by an unusual number of captures by Her Majesty’s cruisers, both in the bights and on the south coast, and also by those by the cruisers of the United States. This year, the capture of only one vessel equipped in the bights, and one with slaves (a transferred Sardinian), on the south coast, have been reported to me—a striking proof of my view.