Radium does not exist free in nature; rather, like uranium, it is melded into the mineral pitchblende. To study radium, the Curies spent countless hours bathed in a radioactive miasma, stirring vats of pitchblende in order to extract infinitesimal amounts of radium. Marie Curie struggled to purify it for medical uses, including early radiation treatment for tumors.

But radium's bluish glow caught people's fancy, and companies in the United States began mining it and selling it as a novelty: for glow-in-the-dark light pulls, for instance, and bogus cure-all patent medicines that actually killed people.

Wristwatches with radium-painted luminous dials became a fad almost overnight. The first large factory to produce the glowing watches, the Radium Luminous Materials Corporation, was opened in 1917, in Orange, N.J. Soon, other companies opened plants in Connecticut and Illinois. Several million radium watches and clocks and instrument dials were made through World War II.

The glowing numerals had to be hand-painted onto the watch dials, a delicate task deemed women's work. Dr. Claudia Clark, a professor of history at Central Michigan University who wrote ''Radium Girls'' (University of North Carolina Press, 1997), said the dial painters worked in ''studios,'' where they mixed their own paint from a powdered base. The workers, some as young as 15, painted about 250 dials a day for a cent and a half apiece, five and a half days a week.

Within a few years, some of the young women became horribly ill from their exposure to radium, and some died. They have become a notorious chapter in the history of occupational disease.

Dr. Clark estimates that 4,000 women were dial painters.

Until sometime in the 1920's, the women were encouraged to use a technique called ''lip-pointing,'' which meant using their lips and tongues to shape their paintbrushes to a fine tip. Not only were their mouths and teeth bathed in radium all day, but the women probably swallowed and inhaled it as well, and they often went home so coated with radioactive paint dust that they glowed in the dark. Unaware of any risk, some painted their lips, teeth, eyelids, fingernails and the buttons on their clothes with the luminous solution.

Meanwhile, more knowledgeable employees in other parts of the plant were beginning to use protective gear and shields when working with radium. And in 1921, while the dial-painting studios were in full swing, Marie Curie visited America and was presented with one gram of radium -- which was enclosed in a 110-pound, lead lined casket.