Jody Dell Seay, age 10,of Houston, Texas, for her question:

Where does radium come from?

Radium is one of several radioactive substances found in the earth's crust. These radioactive substances change from day to day. Every hour, a certain number of their atoms change into atoms of some other substance. Bip atoms of uranium break up into smaller atoms and these smaller atoms break into still smaller atoms. The original uranium changes step by step into a special kind of lead. At one step, it forms atoms of radium. But radium also is radioactive. Right on schedule, its atoms break into smaller atoms of other substances.

The earth's radium is part of a long chain of radioactivity that takes billions of years. It is born and it dies in a rock where other atoms also are changing. Separating it is a hard job and there is never much of it in a rocky ore. We can take it from pitch¬blende or carnotite, autunite or uraninite, or from other rocky ores of uranium. Two hundred tons of the best ore may give us 100 tons of uranium and just one little ounce of radium. No wonder that little bit of radium is worth half a million dollars.