The appearance of a treatise like the present, on a subject on which so many works of merit already exist, may be thought to require some explanation. It might perhaps be sufficient to say, that no existing treatise on Political Ecomony contains the latest improvements which have been made in the theory of the subject. Many new ideas, and new applications of ideas, have been elicited by the discussions of the last few years, especially those on Currency, on Foreign Trade, and on the important topics connected more or less intimately with Colonization: and there seems reason that the field of Political Economy should be re-surveyed in its whole extent, if only for the purpose of incorporating the results of these speculations, and bringing them into harmony with the principles previosly laid down by the best thinkers on the subject.. "