Anti-slavery campaign
Encouraged by publication of Clarkson's essay, an informal committee was set up between small groups from the petitioning Quakers, Clarkson and others, with the goal of lobbying members of parliament (MPs). In May 1787, they formed the Committee for the Abolition of the Slave Trade. The Committee included Granville Sharp as chairman and Josiah Wedgwood, as well as Clarkson. Clarkson also approached the young William Wilberforce, who as an Anglican and an MP was connected within the British Parliament. Wilberforce was one of few parliamentarians to have had sympathy with the Quaker petition; he would soon put a question about the slave trade before the House of Commons, and became known as one of the earliest Anglican abolitionists.
Clarkson took a leading part in the affairs of the Committee for the Abolition of the Slave Trade, and was tasked to collect evidence to support the abolition of the slave trade. Much of the physical evidence he gathered was collected in a wooden chest that made multiple appearances in Parliament as a tangible representation of the slave trade. He faced strong opposition from supporters of the trade in some of the cities he visited. The slave traders were an influential group because the trade was a legitimate and highly lucrative business, generating prosperity for many of the ports.
Liverpool was a major base of slave-trading syndicates and home port for their ships. In 1787, Clarkson was attacked and nearly killed when visiting the city, as a gang of sailors was paid to assassinate him. He barely escaped with his life. Elsewhere, however, he gathered support. Clarkson's speech at the collegiate church in Manchester (now Manchester Cathedral) on 28 October 1787 galvanized the anti-slavery campaign in the city. That same year, Clarkson published the pamphlet A Summary View of the Slave Trade and of the Probable Consequences of Its Abolition.
Clarkson was very effective at giving the committee a high public profile: he spent the next two years travelling around England, promoting the cause and gathering evidence. He interviewed 20,000 sailors during his research. He obtained equipment used on slave-ships, such as iron handcuffs, leg-shackles, and thumbscrews; instruments for forcing open slaves' jaws; and branding irons. He published engravings of the tools in pamphlets and displayed the instruments at public meetings.
Clarkson's research took him to English ports such as Bristol, where he received information from the landlord of the Seven Stars pub. (The building still stands in Thomas Lane.) He also travelled repeatedly to Liverpool and London, collecting evidence to support the abolitionist case.
Clarkson visited The Lively, an African trading ship. Although not a slave ship, it carried cargo of high-quality goods: carved ivory and woven textiles, beeswax, and produce such as palm oil and peppers. Impressed by the high quality of craftsmanship and skill expressed in these items, Clarkson was horrified to think that the people who could create such items were being enslaved. He bought samples from the ship and started a collection to which he added over the years. It included crops, spices and raw materials, along with refined trade goods.
Clarkson noticed that pictures and artefacts could influence public opinion more than words alone. He began to display items from his collection of fine goods to reinforce his anti-slavery lectures. Demonstrating that Africans were highly skilled artisans, he argued for an alternative humane trading system based on goods rather than laborers. He carried a "box" featuring his collection, which became an important part of his public meetings.
He rode some 35,000 miles for evidence and visited local anti-slave-trade societies founded across the country. He enlisted the help of Alexander Falconbridge and James Arnold, two ship's surgeons he had met in Liverpool. They had been on many voyages aboard slave ships, and were able to recount their experiences in detail for publication.
Clarkson also continued to write against the slave trade. He filled his works with vivid firsthand descriptions from sailors, surgeons and others who had been involved in the slave traffic. In 1788 Clarkson published large numbers of his Essay on the Impolicy of the African Slave Trade (1788). Another example was his "An Essay on the Slave Trade" (1789), the account of a sailor who had served aboard a slave ship. These works provided a grounding for William Wilberforce's first abolitionist speech in the House of Commons on 12 May 1789, and his twelve propositions.
Olaudah Equiano (Gustavus Vassa) a member of the Sons of Africa published his memoir, The Interesting Narrative of the Life of Olaudah Equiano, one of the genre of what became known as slave narratives – accounts by slaves who achieved freedom. As an African with direct experience of the slave trade and slavery, Equiano was pleased that his book became highly influential in the anti-slavery movement. Clarkson wrote to the Reverend Thomas Jones (1756–1807) at Trinity College, Cambridge, to introduce Equiano to him and the community. He asked for aid from the Rev. Jones in selling copies of the memoir and arranging for Equiano to visit Cambridge to lecture.
In 1791, Wilberforce introduced the first Bill to abolish the slave trade; it was easily defeated by 163 votes to 88. As Wilberforce continued to bring the issue of the slave trade before Parliament, Clarkson travelled and wrote anti-slavery works. Based on a plan of a slave ship he acquired in Portsmouth, he had an image drawn of slaves loaded on the slave ship Brooks; he published this in London in 1791, took the image with him on lectures, and provided it to Wilberforce with other anti-slave trade materials for use in parliament.
This was the beginning of their protracted parliamentary campaign, during which Wilberforce introduced a motion in favour of abolition almost every year. Clarkson, Wilberforce and the other members of the Committee for the Abolition of the Slave Trade and their supporters, were responsible for generating and sustaining a national movement that mobilised public opinion as never before. Parliament, however, refused to pass the bill. The outbreak of War with France effectively prevented further debate for many years. Henry Dundas, 1st Viscount Melville, who was the Secretary of State for War for prime minister William Pitt the Younger, instructed Sir Adam Williamson, the lieutenant-governor of Jamaica, to sign an agreement with representatives of the French colonists of Saint Domingue, later Haiti, that promised to restore the ancien regime, slavery and discrimination against mixed-race colonists, a move that drew criticism from abolitionists Wilberforce and Clarkson.
By 1794, Clarkson's health was failing, as he suffered from exhaustion. He retired from the campaign and spent some time in the Lake District, where he bought an estate, Eusemere, by Ullswater. There he became a friend of the poet William Wordsworth and Dorothy Wordsworth, his sister.
On 19 January 1796 he married Catherine Buck of Bury St Edmunds, Suffolk; their only child Thomas was born in 1796. They moved to the south of England for the sake of Catherine's health, and settled at Bury St Edmunds from 1806 to 1816. They then lived at Playford Hall, between Ipswich and Woodbridge in Suffolk.
When the war with France appeared to be almost over, in 1804 Clarkson and his allies revived the anti-slave trade campaign. After his ten years' retreat, he mounted his horse to travel again all over Great Britain and canvass support for the measure. He appeared to have returned with all his old enthusiasm and vigour. He was especially active in persuading MPs to back the parliamentary campaign.
Passage of the Slave Trade Act in 1807 ended the trade and provided for British naval support to enforce the law. Clarkson directed his efforts toward enforcement and extending the campaign to the rest of Europe, as Spain and France continued a trade in their American colonies. The United States also prohibited the international trade in 1807, and operated chiefly in the Caribbean to interdict illegal slave ships. In 1808 Clarkson published a book about the progress in abolition of the slave trade. He travelled to Paris in 1814 and Aix-la-Chapelle in 1818, trying to reach international agreement on a timetable for abolition of the trade. He contributed the article on the "Slave Trade" for Rees's Cyclopædia, Vol. 33, 1816. In that same year he was a founder member of a pacifist organisation in London, the Society for the Promotion of Permanent and Universal Peace.
