The letters brought together in this volume have value in that they throw light on the character and early work of a man who was destined to lead an eventful life in the service of science in this country, while at the same time they present a vivid picture of the conditions in California at a time when the first scientific survey of the resources of the state was attempted. To those who had the privilege of association with William H. Brewer during the period of his long connection with Yale University as professor of agriculture in the Sheffield Scientific School, whether as colleagues on the faculty, as students in his classes, or as members of that large body of New England farmers and others who looked to him for guidance on many matters connected with the public welfare, these letters will appeal strongly. The day has passed when men of the Brewer type are met with; men who had broad and encyclopedic minds covering a wide range of thought and action. The rapid growth of science during the past fifty years has brought about a complete change in mental outlook and the successful man of today is the specialist, a master mind in some one field of science. But Brewer was a man whose efforts were extended over a wide range for which he had prepared himself by years of arduous study, and according to the standards of his generation, his preparation was unusually broad and sound. Not only was Brewer thoroughly equipped for the several lines of work he pursued throughout his long life, but in addition he possessed a personality which gave added strength and vigor to all his efforts. A close observer, a careful and sagacious thinker, slow to arrive at a conclusion until all the facts were available, he embodied all those attributes that contribute to success in the conduct of any investigation that calls for wise judgment and logical reasoning. As these letters show, even in his younger days, at the time when he became the “principal assistant” in this survey of California, he it was who had the knowledge and the power to take charge of and carry through a scientific enterprise, under conditions often far from favorable, and without doubt such success as the survey attained was due in no small measure to his resourceful leadership in the field. The record of events contained in these letters, written primarily for the benefit of friends at home, but to be preserved for the possible future needs of the writer, affords the best possible illustration of the character of the man who wrote them. There stand revealed many things that the thoughtful reader will observe, self-sacrifice, devotion to duty, determination to overcome difficulties no matter how great, and above all a serene confidence in his ability to carry through, these and many other characteristics testify to the strength and courage of this man, at a time when he was on the threshold of his scientific career. His later years bear witness to his devotion to scientific truth and its application in various directions for the benefit of mankind.