Released from the navy, he was taken into the service of a slave-dealer on the coast of Africa, at whose hands, and those of the man's negro mistress, he endured every sort of ill-treatment and contumely, being so starved that he was fain sometimes to devour raw roots to stay his hunger.

His constitution must have been of iron to carry him through all that he endured.

In the meantime his indomitable mind was engaged in attempts at self-culture; he studied a Euclid which he had brought with him, drawing his diagrams on the sand, and he afterwards managed to teach himself Latin by means of a Horace and a Latin Bible, aided by some slight vestiges of the education which he had received at a grammar school.

His conversion was brought about by the continued influences of Thomas a Kempis, of a very narrow escape, after terrible sufferings, from shipwreck, of the impression made by the sights of the mighty deep on a soul which, in its weather-beaten casing, had retained its native sensibility, and, we may safely add, of the disregarded but not forgotten teachings of his pious mother.

Providence was now kind to him; he became captain of a slave ship, and made several voyages on the business of the trade.