No disaster that ever befell our country, war not excepted, was in any respect comparable with the horrors which would be incidental to a slave insurrection; yet our people lived during more than half a century in the shadow of that menace. They lived in a state of continual apprehension that it, the most stupendous of conceivable calamities, might at any time overwhelm them. For years patrols had ridden the roads and men had watched of night lest the negroes turn upon their masters. It was, an ever present fear. That the Abolitionists wished the slaves to rise and kill their masters in their beds was a belief widely held in the South and often publicly expressed, and no happening that could be imagined contained a greater possibility of horror and bloodshed.[421] It has been said, and there is great force in the statement, that the "Underground Railroad," instead of working hardship and great loss to slave-holders, was, in reality "the safety-valve to the institution." It was the sluice for the overflow of the dangerous class--the able and discontented. The Underground was organized at the close of the eighteenth century, and had on its rolls more than 30,000 "employees." It carried away from the South, probably 75,000 slaves of the value of more than $30,000,000. The slaves who thus sought and obtained their liberty, taking the risk of arrest and punishment in their attempts to gain it, were the ablest and the most influential among them. Had they remained in slavery, these men would have further developed and become leaders among the slaves, and would have organized them and led them into insurrection. "Had they remained, the direful scenes of San Domingo would have been enacted, and the hot, vengeful breath of massacre would have swept the South as a tornado and blanched the cheek of the civilized world."[422]