unexplored and in few parts of the continent are there people who are likely to appreciate the meaning of any evidence of early times that may come to light. The same is true of

Africa.

Early Discoveries

We have to assume that primitive man used a branch for a club or picked up a stone for a hammer. In time he began to chip off pieces until the core was better fitted to the shape of his hand. He entered then the paleolithic or old stone age which lasted in Europe until about 10,000 years B. C. Then we come to the neolithic age in which the older arts continue, just as man to-day uses a stone to drive a stake, but in which we find some new traits. Among these are the use of bow and arrow, pottery, the hewn ax, a wide employment of bone and horn, while the dog appears as a domestic animal. It is interesting that the first evidence of bow and arrow is a crude cliff drawing in eastern Spain. As the neolithic age matures between 5000 and 6000 B.C., we find tools of stone, ground rather than chipped, the ax, chisel, hammer and maul, but it is not until the end of the era that well-ground and perforated axes are found in Europe. It is more than possible that these were copied from metal axes already in use in Asia. Bronze was used in Spain and Italy by 2500 B.C. and in north Europe about 1900 B.C. Iron appears in Italy about 1100 B.C., in central Europe about 900 B. C., and in north Europe about 500 B.C.

Early Metals

Long prior to these dates we know that advanced civilization existed in Asia and Egypt. Copper was used in Asia at least four or five thousand years before Christ. Seemingly it was the first metal used by man, though gold and silver are very ancient. It is, however, soft and not valuable where cutting edges are desired. Bronze, an alloy of copper and

tin, was in use in Asia and Egypt before 3000 B.C. Where the tin was obtained we do not know. Brass, an alloy of copper and zinc, is much later. Bronze is much harder than either of the component metals and takes a better edge. Iron appears at least two thousand years later than bronze and as an inlay on bronze. There is an added difficulty about iron as it rusts so rapidly that only under the most favorable conditions would any small iron object survive several thousand years. Iron is mentioned only four times in the first four books of the Bible as against eighty-three times for bronze. Our earliest record of the use of iron in Egypt is during the time of Rameses the Great. The later metal culture of the European continent is clearly derived from this older region.

Later Metals

The first metals used by man then were those which occur in relatively pure form in the rocks from which they were taken by a simple process of heating, doubtless discovered by chance, or were found in small masses in the drift as, for instance, gold. They were soft metals with low melting points. Gold may have been the first metal recognized by man. It has always been highly prized. A natural alloy of gold and silver is rather common and was often used for coins by the ancients under the name of elektron. Silver seems to be later and was often more valuable than gold. There is evidence that the method of separating gold from silver was known by 550 B.C. for at that date a gold coinage replaces the elektron in Lydia. As already stated, tin was first used as an alloy of copper. It was not distinguished clearly from lead and was called white lead. Indeed the differences between tin, lead and antimony were not known until A.D. 1450. The iron first used was probably meteoric in origin just as the Greenlanders to-day search for bits to put on their cutting instruments. Mercury was known by

400 B.C. The ancients mixed a zinc ore, calamine, with a copper ore and by heating secured the desired alloy. Early in the Middle Ages pure zinc was known in India and China and pieces were brought to Europe. It was not produced in Europe before A.D. 1700. Bismuth was discovered in the fourteenth century. Platinum was used by the Indians of Central America in small amounts but was not used by the Europeans until the nineteenth century. German silver, an alloy of copper, zinc and nickel, was discovered in China. Prior to the last century only seven metals and a few alloys made from them were of any general service to man. Among these iron has grown steadily in importance and it may be called the metal base of our present civilization. A series of discoveries has given us a number of metals hitherto unknown which are or will be of great value in some instances but most of which are too rare to be of much service to man. One of these, aluminum, is likely to be the metal of the future. Others, like cadmium, chromium, iridium and tungsten, are important in new alloys, most of them having very high melting points. White cast iron melts at 1075° C., chromium at 1587° C., iridium at 2200° C., and tungsten at 3000° C.

Limited Supply of Metals

Metals offer a great contrast to the plants and animals described in the last chapter. They exist only in certain places and fixed quantities and the available amounts are rather limited. Once mined and used much of the metal is so scattered that it can never be recovered. Man faces, therefore, the necessity of finding new sources, of which there is somewhere an end, and the necessity of using the poorer ores for he will use the best first. From the beginning of the Christian Era to the discovery of South America no new source of gold and silver was found. What this meant to the steadily increasing population of Europe the history of

the coinage of the various countries and the search for gold reveals. By contrast these metals were being produced in such amounts at the end of the nineteenth century that money values were being disturbed. On the other hand most of the tin of the world comes from the Dutch East Indies, the older sources are gone, no new supply is in sight and we appear to be facing a world without tin within a comparatively short time. Since man cannot grow new supplies he faces the necessity of substituting some available metal for any which may disappear unless he masters the art of transmutation.

Culture and Invention

Human achievement is always relative. The invention of the bow and arrow was probably as difficult as that of the steam engine. We happen to know the steps taken by the inventors of the latter but the process followed in the first is a matter of speculation. Man can fuse copper and even iron on an open hearth but the production of heat enough to melt tungsten requires a great development in the construction of furnaces and the use of power. Aluminum remains a costly curiosity of little practical value until the electric furnace is devised. Modern surgery turns on new lights and instruments as well as better trained surgeons. In human history, therefore, ere the older metals can be put to many of their present uses, new methods of production must be learned, new processes of manufacture devised. Iron tools such as plows do not replace the older agricultural implements much before the last century and their use was often condemned as impious and it was claimed that they would poison the ground and destroy the crops. Iron, coal and the steam engine are the trinity underlying our civilization.

THE METALS

Iron Supply

Arrhenius estimates that the production of iron in the world in the year 1500 was about 50,000 tons; in 1800, 800,000; in 1900, 41,250,000 reaching a high point of 77,000,000 tons in 1913, dropping then on account of the war. Taking all known supplies and estimating that the rest of the world is as well provided he thinks that 425,000,000,000 tons of iron are available. With the steady increase in consumption assumed not many centuries will pass ere man is conscious of a decrease in the supply. Already he is turning to lower grade ores for not more than 1,300,000 tons of ore having 60 per cent of iron are in sight and of this amount Sweden possesses two-thirds. Arrhenius observes: "But about the metal situation we can only say that man will soon pass from the Age of Heavy Metals to the Age of Light Metals. The light metals, and above all aluminum in the form of its alloys will then replace iron and steel." 1

Pure iron is almost nonexistent. Slosson thus explains its rarity:

Iron is one of the most timid of metals. It has a great disinclination to be alone. It is also one of the most altruistic of the elements. It likes almost every other element better than itself. It has an especial affection for oxygen, and since this is in both air and water, and these are everywhere, iron is not long without a mate. The result of this union goes by various names in the mineralogical and chemical worlds, but in common language, which is quite good enough for our purpose, it is called iron rust.

Not many of us have ever seen iron, the pure metal, soft, ductile and white like silver. As soon as it is exposed to the air it veils itself with a thin film of rust and becomes black and then red. For that reason there is practically no iron in the world except what man has made. It is rarer than gold, than diamonds; we find in the earth no nuggets or crystals of it the size of a fist as we find of these.?