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Dr. Edward N. Lorenz, a meteorologist who tried to predict the weather with computers but instead gave rise to the modern field of chaos theory, died of cancer Wednesday at his home in Cambridge, Mass. He was 90. He is best known for the "butterfly effect," the idea that a small disturbance like the flapping of a butterfly's wings can induce enormous consequences.

Robert T. Hartmann, a close aide to Gerald Ford who drafted many of the president's speeches, including his first address to the nation after President Nixon left office that proclaimed "My fellow Americans, our long national nightmare is over," died Friday of cardiac arrest at Sibley Memorial Hospital in Washington, D.C.. He was 91. NEWS SERVICES