The society was highly successful in raising public awareness and support, and local chapters sprang up throughout Great Britain. Clarkson travelled the country researching and collecting first-hand testimony and statistics, while the committee promoted the campaign, pioneering techniques such as lobbying, writing pamphlets, holding public meetings, gaining press attention, organising boycotts and even using a campaign logo: an image of a kneeling slave above the motto "Am I not a Man and a Brother?", designed by the renowned pottery-maker Josiah Wedgwood. The committee also sought to influence slave-trading nations such as France, Spain, Portugal, Denmark, Holland and the United States, corresponding with anti-slavery activists in other countries and organising the translation of English-language books and pamphlets. These included books by former slaves Ottobah Cugoano and Olaudah Equiano, who had published influential works on slavery and the slave trade in 1787 and 1789 respectively. They and other free blacks, collectively known as "Sons of Africa", spoke at debating societies and wrote spirited letters to newspapers, periodicals and prominent figures, as well as public letters of support to campaign allies. Hundreds of parliamentary petitions opposing the slave trade were received in 1788 and following years, with hundreds of thousands of signatories in total. The campaign proved to be the world's first grassroots human rights campaign, in which men and women from different social classes and backgrounds volunteered to try to end the injustices suffered by others.