IN concluding our labors, there is little need of extended observation. The work of emancipation, in our country, was checked, and the extension of slavery promoted:--first, by the neglect of the free colored people to improve the advantages afforded them; second, by the increasing value imparted to slave labor; third, by the mistaken policy into which the English and American abolitionists have fallen. Whatever reasons might now be offered for emancipation, from an improvement of our free colored people, is far more than counterbalanced by its failure in the West Indies, and the constantly increasing value of the labor of the slave. If, when the planters had only a moiety of the markets for cotton, the value of slavery was such as to arrest emancipation, how must the obstacles be increased, now, when they have the monopoly of the markets of the world? And, besides all this, a more deadly blow, than has been given by all other causes combined, is now levelled at negro freedom from a quarter the least suspected. The failure of the Canadian immigrants to improve the privileges afforded them under British law, proves, conclusively, that the true laws of progress for the African race, do not consist in a mere escape from slavery. We propose not to speak of remedies for slavery. That we leave to others. Thus far this very perplexing question, has baffled all human wisdom. Either some radical defect must have existed, in the measures devised for its removal, or the time has not yet come for successfully assailing the institution. Our work is completed, in the delineation we have given of its varied relations to our agricultural, commercial, and social interests. As the monopoly of the culture of cotton, imparts to slavery its economical value, the system will continue as long as this monopoly is maintained. Slave labor products have now become necessities of human life, to the extent of more than half the commercial articles supplied to the Christian world. Even free labor, itself, is made largely subservient to slavery, and vitally interested in its perpetuation and extension. Can this condition of things be changed? It may be reasonably doubted, whether any thing efficient can be speedily accomplished: not because there is lack of territory where freemen may be employed in tropical cultivation, as all Western and Central Africa, nearly, is adapted to this purpose; not because intelligent free labor, under proper incentives, is less productive than slave labor; but because freemen, whose constitutions are adapted to tropical climates, will not avail themselves of the opportunity offered for commencing such an enterprise.