i2 POPULAR SCIENCE MONTHLY 



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 cer- 

 tain 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 in- 

 sight, greater technical skill and indefatigable industry. 



Note. — Much valuable literature bearing on this and kindred sub- 

 jects will be found in the numerous publications of the U. S. Depart- 

 ment 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 " Bocks, Weathering and Soils," by Dr. 

 Geo. P. Merrill, of the National Museum, is also to be noted. Par- 

 ticularly 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. 



