PRESTON CLOUD

September 26, 1912–January 16, 1991

BY JOHN C. CROWELL

PRESTON ERCELLE CLOUD, JR., eminent biogeologist, paleontologist, and humanist, has left a significant and diverse legacy that cuts across scientific and humanitarian disciplines. As an historical geologist he contributed more than any other single scientist to understanding the evolution of the atmosphere, oceans, and crust of the earth and to understanding the concurrent evolution of life. His work and vision emphasized complex interrelationships through the whole 4.5 billion years of earth history involving the interplay of biological, chemical, and physical processes. His deep delving through these researches led him to a special appreciation of the place of humankind within this evolving environment. He worked diligently to focus attention on the restricted carrying capacity of our planet and for human intelligence to recognize that population increases, limited material and energy resources, and the intergrown complexities of the life-web demand appreciation and action now before the activities of humans lead the planet into calamity. He was a member of the Academy for thirty years and served on its Council and Executive Committee and as chairman of the Geology Section. In many ways he contributed both to the Academy's welfare and to its ser-



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