Here we have the key to the mysteries of all his subsequent career. The denial of the right of petition, the annexation of Texas, the forcing of slavery into the Territories,--these were among the issues upon which he hoped to unite the South in his favor, while retaining enough strength at the North to secure his election. Failing in all his schemes of personal advancement, he died in 1850, still protesting that slavery is divine, and that it must rule this country or ruin it. This is really the sum and substance of that last speech to the Senate, which he had not strength enough left to deliver. We have run rapidly over Mr. Calhoun's career as a public man. It remains for us to notice his claims as a teacher of political philosophy, a character in which he influenced his countrymen more powerfully after he was in his grave than he did while living among them. The work upon which his reputation as a thinker will rest with posterity is his Treatise on the Nature of Government. Written in the last year of his life, when at length all hope of further personal advancement must have died within him, it may be taken as the deliberate record or summary of his political opinions. He did not live to revise it, and the concluding portion he evidently meant to enlarge and illustrate, as was ascertained from notes and memoranda in pencil upon the manuscript. After the death of the author in 1850, the work was published in a substantial and elegant form by the Legislature of South Carolina, who ordered copies to be presented to individuals of note in science and literature, and to public libraries. We are, therefore, to regard this volume, not merely as a legacy of Mr. Calhoun to his countrymen, but as conveying to us the sentiments of South Carolina with regard to her rights and duties as a member of the Union. Events since its publication have shown us that it is more even than this. The assemblage of troublesome communities which we have been accustomed to style "the South," adopted this work as their political gospel. From this source the politicians of the Southern States have drawn all they have chosen to present to the world in justification of their course which bears the semblance of argument; for, in truth, Mr. Calhoun, since Jefferson and Madison passed from the stage, is almost the only thinking being the South has had. His was a very narrow, intense, and untrustworthy mind, but he was an angel of light compared with the men who have been recently conspicuous in the Southern States.