Boaz says, "It seems likely that at a time when the European was still satisfied with rude stone tools, the African had invented or adopted the art of smelting iron. Consider for a moment what this invention has meant for the advance of the human race. As long as the hammer, knife, saw, drill, the spade, and the hoe had to be chipped out of stone, or had to be made of shell or hard wood, effective industrial work was not impossible, but difficult. A great progress was made when copper found in large nuggets was hammered out into tools and later on shaped by melting, and when bronze was introduced; but the true advancement of industrial life did not begin until the hard iron was discovered. It seems not unlikely that the people who made the marvelous discovery of reducing iron ores by smelting were the African Negroes. Neither ancient Europe, nor ancient western Asia, nor ancient China knew the iron, and everything points to its introduction from Africa. At the time of the great African discoveries toward the end of the past century, the trade of the blacksmith was found all over Africa, from north to south and from east to west. With his simple bellows and a charcoal fire he reduced the ore that is found in many parts of the continent and forged implements of great usefulness and beauty."[44] Torday has argued recently, "I feel convinced by certain arguments that seem to prove to my satisfaction that we are indebted to the Negro for the very keystone of our modern civilization and that we owe him the discovery of iron. That iron could be discovered by accident in Africa seems beyond doubt: if this is so in other parts of the world, I am not competent to say. I will only remind you that Schweinfurth and Petherick record the fact that in the northern part of East Africa smelting furnaces are worked without artificial air current and, on the other hand, Stuhlmann and Kollmann found near Victoria Nyanza that the natives simply mixed powdered ore with charcoal and by introduction of air currents obtained the metal. These simple processes make it simple that iron should have been discovered in East or Central Africa. No bronze implements have ever been found in black Africa; had the Africans received iron from the Egyptians, bronze would have preceded this metal and all traces of it would not have disappeared. Black Africa was for a long time an exporter of iron, and even in the twelfth century exports to India and Java are recorded by Idrisi.