28 BULLETIN 618, II. S. DEPARTMENT OF AGRICULTURE. 



107° 10; 



Fig. 10. — Map of the Great Plains area, showing the altitudes above sea level by means of lines follow- 

 ing the contours at 1,000, 1,500, 2,000, 3,000, 4,000, 5,000, and 6,000 feet. 



