Equally unsought and unexpected was his election to the Senate of the United States when absent from the seat of government on a professional errand beyond the sphere of his usual practice. He entered the Senate in the first year of the war with Mexico and held his seat throughout the struggle which ensued over the introduction of slavery into the Territories acquired by the treaty of peace, a struggle which was then threatening the dissolution of the Union; he held his seat during the compromise measures of 1850, under the leadership of Clay; the election of General Taylor; the succession of Fillmore; the election of Pierce and the first half of his term, including the organization of territorial government in Kansas and Nebraska, a period of more fierce, convulsive and (as the sequel has proved) fatal party agitation than any in American history except the years that have succeeded it. Even now, after the dreadful chastening that all have received from recent calamity, it is difficult to recur to it without reviving passions inconsistent with the solemnities of the hour and the charities inspired by common suffering. In this struggle it was maintained on the one hand that inasmuch as these acquisitions of territory had been made by the common contribution of men and means from all the States, the citizens of any State were at liberty to emigrate and settle upon them, and to carry any property they might possess, including slaves; that this was the case by virtue of the operation of the Constitution over the new territory _proprio vigore_. It was further declared that Congress had no authority to legislate in contravention of this right; and, in the progress of the dispute, this latter position, was extended into the assumption that it was the duty of Congress to enact laws to ensure it, and that a failure in this was a breach of Constitutional duty so gross as to justify the injured States in withdrawing from the Union, a power which, it was declared, every State held in reservation, and might exercise at pleasure, the Constitution being but a compact having no sanctions for its perpetuation. On the other hand, there had been for years at the North a party organization, not numerous at first, but which at this period had swollen into a formidable power, whose avowed object was the extinction of slavery; which had denounced the Constitution, so far as it upheld or tolerated it, as a covenant with the infernal powers; had absolved themselves from its maintenance in this particular, and avowed their preference for a disruption of the Union unless slavery should be abolished in the Territories and States as well. More moderate men in that section, while not agreeing with these extremists, denied emphatically either that the Constitution gave to slavery a footing in the Territories or bound Congress to maintain, or not interfere with, its existence there; and that in the exercise of a legislative discretion they might