4
PREFACE.
The very considerable effort involved in such further inquiry was undertaken, with many misgivings, for the Bureau referred to ; and its results have appeared in part in its annual report for the current year. The earnest interest and encouragement of Hon. Carroll D. Wright, chief of the Bureau, who from the first has manifested a deep concern in the investigation of the subject, and the more than generous co-operation of Prof. Clarke, have prompted this attempt to place in a form for more general consideration the facts thus obtained on this subject of daily-increasing importance. I have made free use of the wisdom and experience of others throughout this little monograph, believing that the testimony of many strong ones is better than the assertion of a single observer, which, however careful and veracious, taken alone, might be deemed the overexpression of an enthusiast or specialist. I have not hesitated to speak with directness, or to call things by their right names, believing the cause of truth to be best served thereby. That the subject is full of difficulties, the most casual thinker cannot but perceive. In approaching them I have endeavored to keep both the present