“I surely will not blame them for not doing what I should not know how to do myself. If all earthly power were given me, I should not know what to do, as to the existing institution. ... When, they remind us of their constitutional rights, I acknowledge them, not grudgingly, but fully, and fairly; and I would give them any legislation for the reclaiming of their fugitives, which should not, in its stringency, be more likely to carry a free man into slavery, than our ordinary criminal laws are...