The colonies received some compensations for the restrictions placed upon their industry and commerce. With certain exceptions their trade was free. While some of their products were confined to the British market, they had the monopoly of that market; no Englishman, for example, might buy tobacco which did not come from America or Bermuda. Their export trade to England was encouraged by bounties, and, though their foreign imports generally had to come to them through England, a system of drawbacks, by which the duties were remitted on exportation to America, enabled them to buy continental goods more cheaply than they could be bought in England. Nothing indeed can be further from the truth than the idea that England's treatment of her colonies was harsh or illiberal. Unfortunately the mercantile theory set up an opposition between the interests of a mother-country and her colonies. A far more important mitigation of the restrictions imposed on the colonies than any that came from English liberality, was derived from the constant violation of them. Few English statesmen knew or cared to know anything about colonial affairs. Left to themselves the American colonies grew rich. Their merchants, especially in New England, carried on a brisk and extremely profitable contraband trade. In exchange for lumber, fish, and cattle the New England merchants obtained sugar and molasses, and bullion from the French and Spanish colonies; and vast quantities of rum were distilled in Boston and exported to Africa to be used in the slave trade.