When two metals come together in a molten state, they often form, not a mixture of the two, part copper and part tin, for example, but a new compound, different from either, called an alloy. Copper is, so to speak, a sociable metal, and readily unites with many different metals—amongst others with tin, when it forms bronze, the article that marks a new state in the history of primitive culture. It seems to us strange that an alloy, a combination of two different metals, should have been the first used by man, and not a simple metal like iron. Such, however, is the fact of the case; and we have tried to point out the probable steps which led up to the invention of bronze. We can scarcely comprehend the difficulties which attended the labors of the primitive metal-workers. There were no books containing the wisdom of many, from which the investigator could draw his stores of knowledge. and the only way that knowledge could be disseminated was by word of mouth. Now, when one man makes an important step in a discovery, hundreds of earnest workers, some, perhaps, in distant places, are quickly made aware of the fact, and extend its scope, or point out its imperfections, and thus hasten on the desired end. Then, each individual, or community, must, of necessity, have commenced at the beginning, and the discoveries made would hardly be perpetuated in the memory of others. There were so many obstacles to be overcome before a knowledge of bronze could be acquired, in the then existing state of human knowledge, that it must ever remain a source of wonder to us, at the present day, that it was invented at all. We may picture to ourselves the ancient copper-worker, after numerous experiments, guided by some good genius, finally hitting on some process by which, from his mass of ore, he extracted a nearly pure piece of copper. Having learned how to reduce these ores, there are many ways in which it might have been found that a mixture of the two metals would form a new compound of greatly increased value. It must have taken a long course of experiments to determine what proportions of each metal to use to make the best bronze. It is interesting to know that these early workers had learned the proportions of each to use, not varying a great deal from the results of modern research—that is, from ten to twelve per cent of tin. Bronze relics, no matter where obtained, whether in the Old or the New World, do not widely depart from this standard, and such instances as do would probably denote that the supply of tin became short. This uniformity of composition would imply that the art of making bronze was discovered in one place, from which it gradually spread over the globe.