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ACKNOWLEDGMENTS

The author desires to acknowledge his obligation to the following named persons for the illustrations found on the pages indicated: Director C. E. Thorne, Ohio Experiment Station, 182, 230, 250; Director J. H. Stewart, West Virginia Experiment Station, 112, 176, 177; Director H. J. Wheeler, Rhode Island Experiment Station, 246, 248; President A. M. Soule, North Georgia Agricultural College, formerly Director Tennessee Experiment Station, 206, 216, 217; Director L. H. Bailey, Cornell Experiment Station, 187, 205; Professor F. H. King, Madison, Wisconsin, 62; L. H. Goddard, Ohio Experiment Station, 147, 243, 245; Professor V. H. Davis, Ohio State University, 103; Professor W. J. Frazer, University of Illinois, 159; F. H. Haskett, Columbus, Ohio, 28, 29, and frontispiece; Orange Judd Company, 4, 39, 89, 120, 218. The line drawings are by Orange Judd Company's artist, Mr. B. F. Williamson. Credit for the remaining illustrations, where not cited, is equally divided between Mr. A. B. Graham, Superintendent of Agricultural Extension, Ohio State University, and the author.

This little book is intended primarily for home reading. It is written, however, largely from lecture notes used by the author in a course in soil fertility given to winter course students, and, therefore, will be found to be a suitable text for short courses. It is an attempt to present in non-technical language a subject of great scientific and practical interest to the farmer. The subject of Soil Fertility is so large, that each phase of it could of necessity be only briefly considered in a small book, and the writer did not pretend to make the discussion of any topic exhaustive. For this reason some things have been omitted which might have been discussed with profit in a larger work. Only the more important facts concerning the maintenance of fertility have been presented, but it is believed that the statements so far as they go are in accord with the best scientific thought and practice of the day.

A certain amount of repetition has been purposely used in the text; for it is felt that in this way only can the more important facts be given the emphasis which they deserve, but it is thought that this method of treatment has not been carried to the point of monotony. It is hoped that this book may find a little place in agricultural literature which is not already filled, and that it may be the means of leading a few earnest minds to a more extended study of this important subject of the fertility of the soil.

ALFRED VIVIAN. Ohio State University.

Columbus, Ohio.

PLANT FOOD—ITS NATURE AND SOURCE Running water is Nature's greatest sculptor. It carves out hills and valleys, and carries away the debris to form a soil in

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