From the site:
FROM 1830 to 1850 both Great Britain and the United States, by joint convention, kept on the coast of Africa at least eighty guns afloat for the suppression of the slave trade. Most of the vessels so employed were small corvettes, brigs, or schooners; steam at that time was just being introduced into the navies of the world.
Nearly fifty years ago I was midshipman on the United States brig Porpoise, of ten guns. Some of my readers may remember these little ten-gun coffins, as many of them proved to be to their crews. The Porpoise was a fair sample of the type; a full-rigged brig of one hundred and thirty tons, heavily sparred, deep waisted, and carrying a battery of eight twenty-four-pound carronades and two long chasers; so wet that even in a moderate breeze or sea it was necessary to batten down; and so tender that she required careful watching; only five feet between decks, her quarters were necessarily cramped and uncomfortable, and, as far as possible, we lived on deck. With a crew of eighty all told, Lieutenant Thompson was in command, Lieutenant Bukett executive officer, and two midshipmen were the line officers. She was so slow that we could hardly hope for a prize except by a fluke. Repeatedly we had chased suspicious craft only to be out-sailed.
At this time the traffic in slaves was very brisk; the demand in the Brazils, in Cuba, and in other Spanish West Indies was urgent, and the profit of the business so great that two or three successful ventures would enrich any one. The slavers were generally small, handy craft; fast, of course; usually schooner-rigged, and carrying flying topsails and forecourse. Many were built in England or elsewhere purposely for the business, without, of course, the knowledge of the builders, ostensibly as yachts or traders. The Spaniards and Portuguese were the principal offenders, with occasionally an English-speaking renegade.