the research from which these essays originated. Among persons we wish particularly to thank are Dr. George Shuster, Dr. Donald Mittleman, and The Reverend Ernan McMullin for their encouragement and in many forms their support. We wish finally to acknowledge the versatile assistance of Mrs. Norma Davitt, patient artist of the typescript, and to thank our wives for their constant support and cheerful understanding.
FREDERICK J. CROSSON
KENNETH M. SAYRE