 Slavery was a legal institution in all of the 13 American colonies and Canada (acquired by Britain in 1763).The profits of the slave trade and of West Indian plantations amounted to 5% of the British economy at the time of the Industrial Revolution.A little-known incident in the career of Judge Jeffreys refers to an assize in Bristol in 1685 when he made the mayor of the city, then sitting fully robed beside him on the bench, go into the dock and be fined £1000 for being a 'kidnapping knave'; some Bristol traders at the time were known at the time to kidnap their own countrymen and ship them away as slaves.