Assistance to runaway slaves, always more or less common in the North, was by this time organized into a system. Regular routes, known as "underground railways," were laid out across the free states into Canada, and trusted friends of freedom maintained "underground stations" where fugitives were concealed in the daytime between their long night journeys. Funds were raised and secret agents sent into the South to help negroes to flee. One negro woman, Harriet Tubman, "the Moses of her people," with headquarters at Philadelphia, is accredited with nineteen invasions into slave territory and the emancipation of three hundred negroes. Those who worked at this business were in constant peril. One underground operator, Calvin Fairbank, spent nearly twenty years in prison for aiding fugitives from justice. Yet perils and prisons did not stay those determined men and women who, in obedience to their consciences, set themselves to this lawless work. [Illustration: HARRIET BEECHER STOWE] From thrilling stories of adventure along the underground railways came some of the scenes and themes of the novel by Harriet Beecher Stowe, "Uncle Tom's Cabin," published two years after the Compromise of 1850. Her stirring tale set forth the worst features of slavery in vivid word pictures that caught and held the attention of millions of readers. Though the book was unfair to the South and was denounced as a hideous distortion of the truth, it was quickly dramatized and played in every city and town throughout the North. Topsy, Little Eva, Uncle Tom, the fleeing slave, Eliza Harris, and the cruel slave driver, Simon Legree, with his baying blood hounds, became living specters in many a home that sought to bar the door to the "unpleasant and irritating business of slavery agitation." THE DRIFT OF EVENTS TOWARD THE IRREPRESSIBLE CONFLICT =Repeal of the Missouri Compromise.=--To practical men, after all, the "rub-a-dub" agitation of a few abolitionists, an occasional riot over fugitive slaves, and the vogue of a popular novel seemed of slight or transient importance. They could point with satisfaction to the election returns of 1852; but their very security was founded upon shifting sands. The magnificent triumph of the pro-slavery Democrats in 1852 brought a turn in affairs that destroyed the foundations under their feet. Emboldened by their own strength and the weakness of their opponents, they now dared to repeal the Missouri Compromise. The leader in this fateful enterprise was Stephen A. Douglas, Senator from Illinois, and the occasion for the deed was the demand for the organization of territorial government in the regions west of Iowa and Missouri.