A slave ship carried the equivalent today of hundreds of thousands of pounds worth of trade goods. Indian cotton cloth was the most important part of the cargo, but guns, brassware, glassware, beads, alcohol, tools and trinkets were also traded in exchange for enslaved Africans and the food to feed them on the Transatlantic crossing. Brass making was an important, pioneering industry in Bristol. Brass is an alloy or mixture of copper and zinc. Copper ore came from Cornwall, North Devon and North America. Calamine, a form of zinc, came from the Mendips. Coal came from Kingswood. Output was tied to the African slave trade as much as to domestic markets: brass pots and pans were made especially for the 'Africa trade', such as 'Guinea kettles', 'Guinea neptunes' and 'Guinea manillas'. By the late 1700s copper and brass trade goods were second only to textiles from India and Manchester in terms of slaving cargoes. The slave trader Isaac Hobhouse was also a partner in one of several brass factories in Bristol, so he supplied his own and others' ships with brassware to trade for enslaved Africans.