Curiously enough, the first attack upon the outrageous system of employment which was then common in all parts of the world, was made on behalf of the black slaves of Africa and America. Slavery had been introduced into the American continent by the Spaniards. They had tried to use the Indians as labourers in the fields and in the mines, but the Indians, when taken away from a life in the open, had lain down and died and to save them from extinction a kind-hearted priest had suggested that negroes be brought from Africa to do the work. The negroes were strong and could stand rough treatment. Besides, association with the white man would give them a chance to learn Christianity and in this way, they would be able to save their souls, and so from every possible point of view, it would be an excellent arrangement both for the kindly white man and for his ignorant black brother. But with the introduction of machinery there had been a greater demand for cotton and the negroes were forced to work harder than ever before, and they too, like the Indians, began to die under the treatment which they received at the hands of the overseers. Stories of incredible cruelty constantly found their way to Europe and in all countries men and women began to agitate for the abolition of slavery. In England, William Wilberforce and Zachary Macaulay, (the father of the great historian whose history of England you must read if you want to know how wonderfully interesting a history-book can be,) organised a society for the suppression of slavery. First of all they got a law passed which made "slave trading" illegal. And after the year 1840 there was not a single slave in any of the British colonies. The revolution of 1848 put an end to slavery in the French possessions. The Portuguese passed a law in the year 1858 which promised all slaves their liberty in twenty years from date. The Dutch abolished slavery in 1863 and in the same year Tsar Alexander II returned to his serfs that liberty which had been taken away from them more than two centuries before. In the United States of America the question led to grave difficulties and a prolonged war. Although the Declaration of Independence had laid down the principle that "all men were created free and equal," an exception had been made for those men and women whose skins were dark and who worked on the plantations of the southern states. As time went on, the dislike of the people of the North for the institution of slavery increased and they made no secret of their feelings. The southerners however claimed that they could not grow their cotton without slave-labour, and for almost fifty years a mighty debate raged in both the Congress and the Senate.