No trade required as little outlay in capital as the slave-trade. Trifles, trinkets and refuse stock of every possible kind of merchandise including discarded weapons, were exchanged for the human cargoes on the African coast; who, crowded into vessels, crossed the seas, and upon their arrival in the New World were sold to the colonists who wanted cheap labor and a cheaper service. A fever of speculation which had in it no little touch of adventure, seemed to sweep over England and to delude the people with visions of wealth to be acquired by a conquest of the Spanish possessions from Florida south, including Mexico and Peru. Wild schemes of colonization promised to open Golcondas on the fields of sugar-cane and tobacco, and in the mines holding inestimable treasures of gold and silver. For the realization of those plans negro labor was needed. Even in the West Indies it was welcomed especially by those settlements engaged in the raising of sugar cane. That the Assiento opened the door to all sorts of clandestine commercial operations, as also to insidious political intrigue was soon to become evident. Agents of the Assiento had the right to enter any Spanish port in America and from there send other agents to inland settlements; they had the right to establish warehouses for their supplies, safe against search unless proof of fraudulent operations, that is importations, was incontestable. They could send every year a ship of five hundred tons with a cargo of merchandise to the West Indies and without paying any duty sell these goods at the annual fair. On the return trip this ship was allowed to carry products of the country, including gold and silver, directly to Europe. The assientists urged the American colonies to furnish them supplies in small vessels. Now it was known that such vessels were particularly favored by the smuggling trade. Hence British trade in negro slaves was indirectly used to encourage smuggling and thus undermine Spanish commerce.