Page:Popular Science Monthly Volume 73.djvu/16

12 continues to increase as now, the value of the residue of tillable land which will remain after a few centuries will so appreciate as to force extreme measures for its conservation. The pitiable struggles of certain oriental peoples to retain and cultivate the scant remnants of once ample soils is both an example and a warning. Our escape from such a dire struggle should spring from a clearer forevision, a deeper insight, greater technical skill and indefatigable industry.

Note.—Much valuable literature bearing on this and kindred subjects will be found in the numerous publications of the U. S. Department of Agriculture and the several State Agricultural Stations. Notable among these is the Farmers' Bulletin No. 20 on "Washed Soils," and a special contribution to "Soil Erosion" by W J McGee. The fundamental work on "Rocks, Weathering and Soils," by Dr. Geo. P. Merrill, of the National Museum, is also to be noted. Particularly valuable are the writings of Professor F. H. King on "Soils," "Soil Physics" and "Soil Management," and, especially for the south and west, the work on "Soils," by Professor E. W. Hilgard.