This book is designed to be primarily a history of research facts, measurements, and ideas and the people who developed them. ''Research'' is defined very broadly to include from bench-top laboratory experiments to worldwide environmental investigations. The book is not a monograph or a critical review. The findings and conclusions are presented largely as the investigators saw and reported them. Frequently, the discussion utilizes the terminology and units of the time, unless they are truly antiquated or potentially unclear. It is only when the work being reported is markedly iconoclastic or obviously wrong that I chose to make special note of it or to correct it. Nevertheless, except for direct quotations, the language is mine, and I take full responsibility for it. The working materials for this volume included published papers in scientific journals, books, published conferences and symposia, personal interviews with over 100 individuals, some of them more than once (see Appendix A), and particularly for the 1940--1950 decade and for the large government-supported laboratories to the present day, ''in-house'' reports. These reports frequently represent the only comprehensive archive of what was done and why. Unfortunately, this source is drying up because of storage problems and must be retrieved …