When did man first begin to use iron? The answer seems self-evident: when he learned to smelt iron from its ore.

   Historians have even established the approximate date of this great event, the date of the beginning of the "Iron Age" on Earth. But actually the Iron Age started before the primeval metallurgists produced the first kilogram of iron in the primitive blast furnace. Such was the conclusion drawn by the chemists armed with mighty methods of analysis.

   The first pieces of iron used by our antecedents literally fell from the sky. What we call iron meteorites always contain nickel and cobalt besides iron. Now when analysing some of the most ancient iron tools chemists found them to contain iron's neighbours in the Mendeleyev Table, namely, cobalt and nickel. These metals are by no means always present in the iron ores on Earth.

   Is this conclusion quite unquestionable? Not a hundred per cent, anyway. The study of antiquity is a very difficult matter. But here one is very likely to come up against the unexpected.

   Archeologists once sprang the following surprise on the historians of chemistry. In 1912, while carrying on excavations among ancient Roman ruins near Naples, Professor Günther of Oxford University found some glass mosaics of surprising beauty. The colour of the glass did not seem to have faded in two thousand years.

   To establish the composition of the colouring matter used by the ancient Romans Günther sent two samples of pale green glass to England where they fell into the hands of the chemist Maclay. The analysis showed nothing unexpected, not to mention some impurity amounting to about one and a half per cent.

   But what this impurity was, Maclay could not say.

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