For assistance with photographs and biographical information, I thank those scientists who graciously responded to my requests and the many libraries and archives who helped. I would also like to express my gratitude to the University of Montana Mansfield Library, where much of the research for this book was completed, and to the authors of the many science reference books I consulted. Finally, my sincerest thanks to Frank K. Darmstadt, Executive Editor, Melissa Cullen-DuPont, Assistant Editor, and Alana Braithwaite, Editorial Assistant, for their unwavering support and superb guidance throughout the project.