Radioactive Elements "Descend" from One Another

Thus the radio elements formed strange and cruel families in which each member was created by spontaneous transformation of the mother substance: radium was a “descendant” of uranium, polonium a descendant of radium.

 1889 Prediction That Has Almost Come True

We may indeed live yet to see, or at least we may feel some confidence that those who come after us will see, such bodies as oxygen and hydrogen in the liquid, perhaps even in the solid state, and the question of their metallic or non-metallic nature thereby finally settled.