Washington University in St. Louis played host to the 1904 World's Fair and Brookings Hall , pictured at left, served as its administrative center. Just behind Brookings is Holmes Lounge, where last week the university played host to an annual conference of headmasters. In 1904 Holmes housed the Convocation of Arts and Sciences for the World's Fair. It was said at the time that all the knowledge known to man was presented in this hall. It was in this hall that I met Mark Wrighton, Chancellor of Washington University. He spoke with conviction about the greatest issue he felt confronts us--clean, renewable energy. With a population of the planet expected to reach 9 billion by mid-century, the chancellor argued, combined with industrialization of underdeveloped economies in China and India as just two examples, energy use will double and the need for clean, reliable energy will be the defining issue of this new century. It is directly tied to our security, he said,