PREFACE 
Carnegie Institution; and Professor Ralph S. Tarr of Cornell 
University. To Messrs. Gregory, Keller, and Bishop of Yale 
University the author is indebted for permission to use, in 
slightly modified form, several maps from their * Physical and 
Commercial Geography”; these are Physiographic Regions of 
the United States, New York Harbor and its Approaches, and 
the maps showing the ocean routes of the world and the routes 
and centers of ancient commerce. Several of the maps show- 
ing distribution of crop and livestock production have been 
taken from V. C. Finch and O. E. Baker's “ Geography of 
the World's Agriculture.” Many government bureaus and the 
officers of several agricultural experiment stations have rendered 
generous assistance. 
ALBERT PERRY BRIGHAM