Attrition was the inevitable result of any slaving voyage. There would always be deaths; it was just a question of numbers. The deaths were frequent enough, however, that the crewmen of slavers often told of the schools of sharks that followed their ships all the way from Africa to their final destination. Much has been written about the horrors of the infamous Middle Passage - the voyage from Africa to America, Brazil, or the islands of the Caribbean - so called because it represented the second leg of a 3-part trip by the slaver: from home in the United States or Europe to Africa for the cargo of slaves; then from Africa to the place of sale; and finally, home again. The Middle Passage took anywhere from several weeks to 3 months. Debilitated, often already ill and half-starved from the trek from the African interior to the coast and the waiting slave ship, the Africans
"are packed below in as dense a mass as it is possible for human beings to be crowded; the space allotted them being…about four feet high between decks, there, of course, can be but little ventilation given. These unfortunate beings are obliged to attend to the calls of nature in this place - tubs being provided for the purpose - and here they pass their days, their nights, amidst the most horribly offensive odors of which the mind can conceive, and this under the scorching heat of the tropical sun, without room enough for sleep; with scarcely space to die in; with daily allowance of food and water barely sufficient to keep them alive. The passage varies from forty to sixty days, and when it has much exceeded the shorter time disease has appeared in its most appalling forms, the provisions and water are nearly exhausted, and their sufferings are terrible."

All ships at sea had their own cacophony of sounds: the wind in the sheets and sails, the groan and crack of wood driven by water and weather, the commands of the officers shouting to be heard above it all, and the responding cries of the crew. Aboard a slaver, the perpetual groans and pleadings of hundreds of desperate, often dying humans were added as well. In 1854, the slaver Captain Theodore Canot, a contemporary of Gordon, recorded his memoirs of a lifetime of trafficking in humans. He tells of the ship Volador, which lost 136 of its 747 captives:
"The degree of mortality was not unusual; neither was the overcrowding. The slaves were laid on their sides, spoon-fashion, the bent knees of one fitting into the hamstrings of his neighbour. On some vessels, they could not even lie down; they spent the voyage sitting in each other's laps. The stench was terrific. A British officer testified that one could smell a slaver 'five miles down wind.'"

The death rate among the captives varied, depending on the length of the voyage, the severity of conditions on board, and the callousness of captain and crew. It averaged 17.5% among captured American slavers for the 20-year period 1844-1864; out of every 1000 Africans shipped as slaves, approximately 175 perished. Captives died of disease, thirst, starvation, suffocation, exhaustion, suicide, and sometimes, simply despair. If a captive attempted suicide and failed, he or she would be mutilated, tortured or executed, to provide an example for the others. Should slaves revolt against the horrific conditions, they would be summarily hanged, shot, or drowned. Between the high rate of mortality aboard ship and that of the slave in his first year ashore - the period of adjustment to a slave's existence that the owners euphemistically called "seasoning" - nearly one in every three people taken from Africa in bondage would die during the process of enslavement.

In 1847, the Brig Senator boarded 900 slaves. The first night, 74 died of suffocation. Before the three weeks' voyage was done, more than 200 additional captives had perished of thirst. The Senator eventually delivered only 600 of her slaves to Brazil. Through neglect and cruelty, one-third had died.

Commanded by Captain Luke Collingwood, the British ship Zong picked up 400 African slaves, and set sail for Jamaica on September 6, 1781. Within two and a half months, he had lost 60 captives; several more were ill, and he was running short of water. If the slaves were to die on their own, the ship's owners would take the loss. However, if they were thrown over the side while living, it could be claimed that they were washed overboard. This would be attributed to "perils of the sea," and the insurance company would have to pay. Consequently, the captain selected 54 sick slaves, and cast them overboard, living and bound. Two days later, he followed with another 42. That day, it rained, providing the ship with enough water for 11 days. Nonetheless, Collingwood threw 26 more into the sea, bound at the wrists. As he was about to prepare another ten for a like fate, they elected to take their own lives and jumped overboard. The underwriters of the voyage, suspicious, refused to honor the insurance policy. The ship owners sued them, and the British courts obliged them to pay the premium.

Stories abound of slaver captains who chose to jettison their cargo rather than face fine, imprisonment, or forfeiture of their vessels. One such slaver, an Englishman named Homans, had already completed 10 successful voyages, delivering around 5000 Africans to the shores of Brazil and Cuba. On the return of his eleventh voyage, he found his brig, the Brillante, surrounded by four cruisers. He immediately had his cargo of 600 manacled captives herded to the rail and bound to the anchor chain. When the cruisers' boats lowered and made for the Brillante, Homans had the anchor thrown over side; it plummeted to the ocean floor, carrying every man, woman and child with it. When the warships' crew boarded the Brillante, they found clear evidence that several hundred human beings had occupied the hold only moments before, but they could do nothing. They were forced to release the brig, as Homans "jeered in their faces and defied them as they stood on his deck."

What would allow for such a callous disregard for life? Greed. In fact, a successful slaving voyage was profitable beyond all reason. It has been estimated that during the mid-1800's, when Nathaniel Gordon was pursuing his career, a slave purchased in Africa for approximately $40 worth of trade goods would bring a price ranging from $400 to $1200. Therefore, the selling price of a cargo of, say, 800 slaves ranged between $320,000 and $960,000. Even after factoring in the cost of outfitting the ship, paying - and paying off - all the people involved in the voyage, and the inevitable loss of "inventory," a successful slaving expedition realized a profit many times in excess of the initial investment. Consider that $100 in the 1850's would be worth around $4000 today, and the allure of such a venture becomes apparent. Given such returns, a single successful trip could more than compensate for three or four previous failures, and make the fortunes of investors and captain.