In precisely one month from the delivery of these words by the President an ominous movement was made in Congress. Notwithstanding all the vows of fealty to the Compromise of 1850, the pro-slavery leaders of the South were not contented with the aspect of affairs. The result of the Mexican war had deeply disappointed them. Its most striking political effect thus far was the addition to the Union of a large and imposing free State on the Pacific,--an empire indeed in prospective wealth and power. In the battle between free institutions and slave institutions, California represented a strong flank movement threatening destruction to slavery. Her vote in the Senate gave a majority of two to the free States. The equality of the sections had been steadily maintained in the Senate since the admission of Louisiana in 1812. The break now was ominous; the claim of equality had been disregarded; the superstition which upheld it was dispelled, and the defenders of slavery could see only a long procession of free States marching from the North-West to re-enforce a power already irresistibly strong. From what quarter of the Union could this anti-slavery aggression be offset? By what process could its growth be checked? Texas might, if she chose to ask for her own partition, re-enforce the slave-power in the Senate by four new States, as guaranteed in the articles of annexation. But the very majesty of her dimensions protested against dismemberment. Texas was as large as France, and from the Sabine to the Rio Grande there was not a cotton-planter or a cattle- herder who did not have this fact before his eyes to inflame his pride and guide his vote against parting with a single square mile of her magnificent domain. New Mexico and Utah were mountainous and arid, inviting only the miner and the grazier and offering no inducement for the labor of the slave. The right guaranteed to these territories in the Compromise of 1850 to come in as slave States was, therefore, as Mr. Webster had maintained, a concession of form and not of substance to the South. Seeing slavery thus hemmed in on all sides by nature as well as law, and sincerely believing that in such a position its final extinction was but a question of time, the Southern leaders determined to break the bonds that bound them. From their own point of reasoning they were correct. To stand still was certain though slow destruction to slavery. To move was indeed hazardous, but it gave them a chance to re-establish their equality in the administration of the government, and for this they determined to risk every thing.