Having thus gained practically free admittance to the field, English merchants sought to exclude other nations by securing a monopoly of the lucrative Spanish colonial slave-trade.  Their object was finally accomplished by the signing of the Assiento in 1713.[8]

The Assiento was a treaty between England and Spain by which the latter granted the former a monopoly of the Spanish colonial slave-trade for thirty years, and England engaged to supply the colonies within that time with at least 144,000 slaves, at the rate of 4,800 per year.  England was also to advance Spain 200,000 crowns, and to pay a duty of 331/2 crowns for each slave imported.  The kings of Spain and England were each to receive one-fourth of the profits of the trade, and the Royal African Company were authorized to import as many slaves as they wished above the specified number in the first twenty-five years, and to sell them, except in three ports, at any price they could get.

It is stated that, in the twenty years from 1713 to 1733, fifteen thousand slaves were annually imported into America by the English, of whom from one-third to one-half went to the Spanish colonies.[9] To the company itself the venture proved a financial failure; for during the years 1729-1750 Parliament assisted the Royal Company by annual grants which amounted to L90,000,[10] and by 1739 Spain was a creditor to the extent of L68,000, and threatened to suspend the treaty.  The war interrupted the carrying out of the contract, but the Peace of Aix-la-Chapelle extended the limit by four years.  Finally, October 5, 1750, this privilege was waived for a money consideration paid to England; the Assiento was ended, and the Royal Company was bankrupt.

By the Statute 23 George II., chapter 31, the old company was dissolved and a new “Company of Merchants trading to Africa” erected in its stead.[11] Any merchant so desiring was allowed to engage in the trade on payment of certain small duties, and such merchants formed a company headed by nine directors.  This marked the total abolition of monopoly in the slave-trade, and was the form under which the trade was carried on until after the American Revolution.

That the slave-trade was the very life of the colonies had, by 1700, become an almost unquestioned axiom in British practical economics.  The colonists themselves declared slaves “the strength and sinews of this western world,"[12] and the lack of them “the grand obstruction"[13] here, as the settlements “cannot subsist without supplies of them."[14] Thus, with merchants clamoring at home and planters abroad, it easily became the settled policy of England to encourage the slave-trade.  Then, too, she readily argued that what was an economic necessity in Jamaica and the Barbadoes could scarcely be disadvantageous to Carolina, Virginia, or even New York.  Consequently, the colonial governors were generally instructed to “give all due encouragement and invitation to merchants and others, ... and in