Inquiry immediately makes it clear that man must first have come to know iron through meteorites. Except for the great masses at Ovifak in Greenland, which are outside the question, iron from earthly sources is not known to occur in the native state. It does, however, occur in metallic form in meteorites (FIG. 2) and is the only metal to do so. In this form it may be found in solid lumps of metal weighing as much as 50 tons (Bacubirito), 36½ tons (Ahnighito), or 15⅔ tons (Chupaderos). But of course most of it occurs in much more manageable sizes—in pieces as large as a man’s head, a hen's egg, a pea, or only as dust. But all meteorites are not solid iron, Very many are a mixture of iron and stone (FIGS. 1, 3) or what is to all intents and purposes merely stone (FIG. 4), and so useless to man as a source of iron. All meteorites fall into one of these three classes.