In connexion with our discussion of electricity (Chapter XIII) we spoke of the special function of the metals as bearers of the 'mercurial' quality (in the alchemical sense of the term). As one of the characteristics which reveal this function we mentioned the peculiar capacity of metals to behave as 'solid fluids'. This exceptional place among the mineral substances of the earth, the metals owe to their close association with the extra-terrestrial astral forces of the world. In this field, too, modern spiritual investigation has recovered something which was known to people of old - that among the metals there are seven which have a distinctive character, for each stands in a special relation to one of the seven planets (that is, the planetary force-spheres) of our cosmic system. This is shown in the following table:

 Saturn Lead Jupiter Tin Mars Iron Sun Gold Venus Copper Mercury Quicksilver Moon Silver