Slavery, unhappily, exists within the United States. Enlightened men, in the States where it is permitted, and everywhere out of them, regret its existence among us, and seek for the means of limiting and of mitigating it. The first introduction of slaves is not imputable to the present generation, nor even to their ancestors. Before the year 1642, the trade and ports of the colonies were open to foreigners equally as those of the mother country; and as early as 1620, a few years only after the planting of the colony of Virginia, and the same year in which the first settlement was made in the old colony of Plymouth, a cargo of negroes was brought into and sold as slaves in Virginia by a foreign ship. From this beginning, the importation of slaves was continued for nearly two centuries. To her honor, Virginia, while a colony, opposed the importation of slaves, and was the first State to prohibit the same, by a law passed for this purpose in 1778, thirty years before the general prohibition enacted by Congress in 1808. The laws and customs of the States in which slavery has existed for so long a period, must have had their influence on the opinions and habits of the citizens, which ought not to be disregarded on the present occasion. * * * * * When the general convention that formed the Constitution took this subject into their consideration, the whole question was once more examined; and while it was agreed that all contributions to the common treasury should be made according to the ability of the several States to furnish the same, the old difficulty recurred in agreeing upon a rule whereby such ability should be ascertained, there being no simple standard by which the ability of individuals to pay taxes can be ascertained. A diversity in the selection of taxes has been deemed requisite to their equalization. Between communities this difficulty is less considerable, and although the rule of relative numbers would not accurately measure the relative wealth of nations, in States in the circumstances of the United States, whose institutions, laws, and employments are so much alike, the rule of numbers is probably as near equal as any other simple and practical rule can be expected to be (though between the old and new States its equity is defective),--these considerations, added to the approbation which had already been given to the rule, by a majority of the States, induced the convention to agree that direct taxes should be apportioned among the States, according to the whole number of free persons, and three-fifths of the slaves which they might respectively contain.