After the long use of stone, man gradually became acquainted with some of the metals, and subsequently discovered the method of combining copper with tin and other alloys to form bronze, which material, to a large extent, added to the implements already in use. The Bronze Age is the most hypothetical of all these divisions, as it does not appear to have been as universal as the Stone, on account of the difficulty of obtaining metals. The use of copper by the Indians of the Lake Superior region was a very marked epoch in their development, and corresponds to the Bronze Age of other nations, although their advancement in other particulars appears to be less than that of other tribes of European origin which used bronze freely. Bronze implements have been found in great plenty in Scandinavia and Peru, and to a limited extent in North America. They certainly mark a stage of progress in advance of that of the inhabitants of the Stone Age. Bronze {37} was the chief metal for implements throughout the early civilization of Europe. Following the age of bronze is the Iron Age, in which the advancement of man is especially marked. The bronze implements were at first supplemented in their use by those of iron. But gradually iron implements superseded the bronze. The Iron Age still is with us. Possibly it has not yet reached its highest point. Considering the great structures built of iron, and the excessive use of iron in machinery, implements, and furniture, it is easy to realize that we are yet in this great period. Though we continue to use stone more than the ancients and more bronze for decoration and ornament than they, yet both are subordinate to the use of iron. General as the above classification is, it helps in an indefinite way to give us a central idea of progress and to mark off, somewhat indefinitely, periods of development. _The Development of Art_.--Utility was the great purpose underlying the foundation of the industrial arts. The stone axe, or celt, was first made for a distinct service, but, in order to perfect its usefulness, its lines became more perfect and its surface more highly polished. So we might say for the spear-head, the knife, or the olla. Artistic lines and decorative beauty always followed the purpose of use. This could be applied to all of the products of man's invention to transform parts of nature to his use. On account of the durability of form, the attempt to trace the course of civilization by means of the development of the fine arts has met with much success. Though the idea of beauty is not essential to the preservation of man or to the making of the state, it has exerted a great influence in individual-building and in society-building. In our higher emotional natures aesthetic ideas have ruled with imperial sway.