In 1695 an Englishman - Captain Davis - was made a burgess of Glasgow due to his knowledge of Africa. However, it was not until 1719 that two Port Glasgow brigs – the Loyalty and Hannover - were dispatched to trade in slaves on the coast of West Africa. The Bogle family provided the common link in the two circles of Glasgow merchant adventurers that fitted them out. The vessels, their cargoes from Guinea and principal officers were, however, taken over by the Scots network in London.
Both voyages proved financial disasters. The Loyalty limped home after being attacked by three pirate vessels off the Guinea coast, her cargo looted and skilled crewmen abducted. The Hannover, after a series of delays and incidents, acquired 134 enslaved Africans, mainly at Old Calabar, now in eastern Nigeria. A quarter of their number died during an extended middle passage to Barbados. The majority of survivors were sold at St Kitts, in the West Indies, under the instructions of the trusted resident Scots planter Colonel William McDowall (later of Shawfield Mansion and Castle Semple estate Renfrewshire).
Alexander Horsburgh, the surgeon and the supercargo of the Hannover, was arrested and imprisoned on his return on charges of fraud and gross negligence brought by the owners. His role as "supercargo" gave him responsibility for the cargo, all commercial transactions and direction of the voyage. After a protracted and acrimonious trial at the High Court of Admiralty sitting in Edinburgh he was acquitted. Thereafter, the Glasgow merchant community abandoned the supercargo model of transatlantic trading and direct slaving out of the Clyde. They did, however, continue to be involved as minority shareholders in Liverpool slavers.