It not only worked against a return by New England from manufacturing to commerce, but it soon brought into the ranks of protectionists a northern and western agricultural element that had been accustomed to sell surplus products to West Indian planters seeking cheap food-stuffs for their slaves.

This new protectionist element was as yet not crystallized into a clamour for "home markets" for agriculture, but the pressure of opinion was beginning to be felt, and by 1820 the question of West Indian trade became one of constant agitation and demanded political action.

That action was taken on lines of retaliation.

Congress in 1818 passed a law excluding from American ports any British vessel coming from a port access to which was denied to an American vessel, and placing under bond in American ports British vessels with prohibition of their proceeding to a British port to which American vessels could not go.

This act affected not merely direct trade with the West Indies, but stopped the general custom of British ships of taking part cargoes to Jamaica while _en route_ to and from the United States.