But Zachary had signed on with a mind to learning the sailor's trade, and he stepped on board with great eagerness, carrying a canvas ditty-bag that held little more than a change of clothes and a penny-whistle that his father had given him as a boy. The Ibis provided him with a quick, if stern schooling, the log of her voyage being a litany of troubles almost from the start. Mr Burnham was in such a hurry to get his new schooner to India that she had sailed short-handed from Baltimore, shipping a crew of nineteen, of whom nine were listed as 'Black', including Zachary. Despite being undermanned, her provisions were deficient, both in quality and quantity, and this had led to confrontations, between stewards and sailors, mates and fo'c'slemen. Then she hit heavy seas and her timbers were found to be weeping: it fell to Zachary to discover that the 'tween-deck, where the schooner's human cargo had been accommodated, was riddled with peepholes and air ducts, bored by generations of captive Africans. The Ibis was carrying a cargo of cotton, to defray the costs of the journey; after the inundation, the bales were drenched and had to be jettisoned.

Off the coast of Patagonia, foul weather forced a change in course, which had been plotted to take the Ibis across the Pacific and around Java Head. Instead, her sails were set for the Cape of Good Hope – with the result that she ran afoul of the weather again, and was becalmed a fortnight in the doldrums. With the crew on half-rations, eating maggoty hardtack and rotten beef, there was an outbreak of dysentery: before the wind picked up again, three men were dead and two of the black crewmen were in chains, for refusing the food that was put before them. With hands running short, Zachary had put aside his carpenter's tools and become a fully fledged foretopman, running up the ratlines to bend the topsail.