To gather evidence against the Slave Trade, Clarkson rode 35,000 miles and boarded hundreds of ships. He interviewed over 20,000 people including seamen, merchants and ships' surgeons, in taverns and on the quayside, and collected many items that he kept in a specially made box.
In early 1787, Thomas Clarkson was aware that he needed hard facts to support his arguments for abolishing the Slave Trade. To gather this evidence, he travelled to the port of London, followed by the large slaving centres of Bristol and Liverpool.
In the port of London, there were ships loaded with cargoes such as cloth, guns, ironware and drink that had been manufactured in Britain. They were ready to leave for the African coast, where the goods would be traded for for slaves.
At the ports Thomas Clarkson visited, there were also African trading vessels loaded with cotton, indigo, tobacco, oils, waxes and gums, spices and woods, gold and ivory, ready for the markets in Britain. It occurred to Clarkson that there was plenty of opportunity for a trade with Africa, other than the trade in human beings.
One ship, however, that filled him with horror was the slave ship, the Fly. When saw the dark hold in which the enslaved people had been packed, covered by a grill or grating, he became too upset to continue. The conditions that the enslaved people had to endure on ships such as these, filled him with such sadness and anger, that he quickly left the ship.
He also talked to many involved in the trade, including sailors and merchants, and uncovered some shocking statisitcs on what life was like for the sailors, as well as the enslaved Africans. In Bristol, for example, he met two surgeons who had worked on the slave ships, James Arnold and Alexander Falconbridge (see document below). They both gave him detailed descriptions of life on the slave ships. Whilst in Bristol, Thomas Clarkson also made contact with a Mr Thompson, landlord of the Seven Stars, who acted as a guide on Clarkson visit to taverns in the area to collect evidence. An interesting article about Clarkson's association with the landlord of the Seven Stars, can be seen in the document attachments below.
Talking to people in the trade was a dangerous occupation. One day, in 1787, whilst visiting Liverpool, he looked up to see a group of about eight seamen approaching. He tried to walk away but they surrounded him. Realising the threat to his life, he struggled to free himself. He recorded in his journal:
"I darted forward, one of them, against whom I pushed myself, fell down. Their ranks were broken and I escaped, not without blows, amidst their imprecations and abuse."
In 1788, Clarkson set out on another tour, covering 1600 miles in just two months. At Plymouth he uncovered a key piece of evidence, the plan and section of a loaded slave ship. Clarkson reworked the plan in London, applying the idea to the Brookes (a slave ship from Liverpool). The resulting image was one of the most effective pieces of evidence produced and shocked many who saw it.
Clarkson's aims were to:
The task was enormous. In 1790, Clarkson visited over 317 ships in an effort to track down a seaman, who had apparently witnessed atrocities in Africa. He talked to over 3000 sailors, until he finally found Isaac Parker, in Plymouth, on the frigate Melampus. Parker was a respected and honest seaman. He provided evidence of slave poaching off the African coast, between the Calabar and Bonny rivers.
Clarkson's travels across the country encouraged the setting up 1,200 branches for the Abolition of the Slave Trade and the beginnings of a mass anti-slavery movement. After the 1807 act was passed, Thomas Clarkson continued to campaign against slavery.
In 1823, a new group was formed, supported by Clarkson, Buxton and Wilberforce, that aimed to abolish slavery in the British Colonies. At the age of 63 Clarkson went on another national tour, covering 10,000 miles, visiting every county in England, Scotland and Wales in order to raise support for the cause.