"Shortly after the Declaration of Independence, the Northern States adopted prospective measures to relieve themselves of the African population. But it is a great mistake to suppose that their policy in this particular was prompted by any spirit of philanthropy or tender regard for the welfare of the negro race. On the contrary, it was dictated by an enlightened self-interest, yielding obedience to overruling laws of social economy. Experience had shown that the African race were not adapted to high northern latitudes, and that slave labour could not compete successfully with free white labour in those pursuits to which the industry of the North was directed. This discovery having been made, the people of the North, at an early day, began to dispose of their slaves by sale to citizens of the Southern States, whose soil, climate, and productions were better adapted to their habits and capacities; and the legislation of the Northern States, following the course of publick opinion, was directed, not to emancipation, but to the removal of the slave population beyond their limits. To effect this object, they adopted a system of laws which provided, prospectively, that all slaves born of female slaves, within their jurisdiction, after certain specified dates, should be held free when they attained a given age. No law can be found on the statute-book of any Northern State, which conferred the boon of freedom on a single slave in being. All who were slaves remained slaves. Freedom was secured only to the children of slaves, born after the days designated in the laws; and it was secured to them only in the contingency that the owner of the female slave should retain her within the jurisdiction of the State until after the child was born. To secure freedom to the afterborn child, therefore, it was necessary that the consent of the master, indicated by his permitting the mother to remain in the State, should be superadded to the provisions of the law. Without such consent, the law would have been inoperative, because the mother, before the birth of the child, might, at the will of the master, be removed beyond the jurisdiction of the law. There was no legal prohibition of such removal, for such a prohibition would have been at war with the policy of the law, which was obviously removal, and not emancipation. The effect of this legislation was, as might have readily been foreseen, to induce the owners of female slaves to sell them to the planters of the South, before the time arrived when the forfeiture of the offspring would accrue. By these laws, a wholesale slave trade was inaugurated, under which a large proportion of the slaves of the Northern States were sold to persons residing south of Pennsylvania; and it is an unquestionable fact that a large number of the slaves of the Southern States are the descendants of those sold by Northern men to citizens of the South, with covenants of general warranty of title to them and to their increase."