For several years the attention of Mr. Colton had been more and more attracted to the literature and philosophy of political economy. In 1846 he printed his first work in which it is formally treated, _The Rights of Labor_, in which he asserted, illustrated, and with unanswerable logic vindicated the American doctrine of the privileges and dignity of Industry; and in 1848 he gave to the world his last and most important work, _Public Economy for the United States_. From the formation of the first system of society the subjects embraced in this production have employed the most powerful intellects of all nations. But though illustrated by the liveliest genius and the profoundest reflection, they have not until recently assumed even the forms of science. We cannot tell what formulæ of economical truth passed from existence in the lost books of Aristotle. The father of the peripatetic philosophy undoubtedly brought to public economics the severe method which enabled him to construct so much of the everlasting science of which the history goes back to his times; but whatever direction he gave to the subject, by the investigation of its ultimate principles and their phenomena, his successors, and the writers upon it since the revival of learning, have generally been guided by empirical laws, which in an especial degree have obtained in regard to the economy of commerce. Scarcely any of the literature or reflection upon the subject has gone behind the bold hypotheses of free trade theorists, which have been as unsubstantial as the fanciful systems of the universe swept from existence by the demonstrations of Newton. Not only have economical systems generally been made up of unproven hypotheses, but they have rarely evinced any such clear apprehension and constructive ability as are essential in the formation and statement of principles; and down to the chaos of Mr. Mills's last essay there is scarcely a volume on political economy which rewards the wearied attention with any more than a vague understanding of the shadowy design that existed in the author's brain.