MORE than two hundred years have elapsed since the first cargo of slaves was landed on the banks of the James River, in the colony of Virginia, from the West coast of Africa. From the introduction of slaves in 1620, down to the period of the separation of the Colonies from the British Crown, the number had increased to five hundred thousand; now there are nearly four million. In fifteen of the thirty-one States, Slavery is made lawful by the Constitution, which binds the several States into one confederacy.