LIST OF ILLUSTRATIONS 



Page 



1. Physical Features of North America Frontispiece 



2. Precipitation Zones of the World 



3. Map Showing the Northern Limits of some 



crops and trees 7 



4. Nature's Map of the Prairie Provinces 



5. Precipitation Zones in Canada - 14 



6. Average Annual Precipitation - 15 



7. Monthly Distribution of Precipitation in 



Canada - 16 



8. Monthly Distribution of Precipitation at 



Different Representative Points - 17 



9. Precipitation at Swift Current, Sask. 18 



10. Average Depth of Snowfall in Western 



Canada - ID 



11. Variations from Normal Precipitation 22 



12. Temperature Zones of Canada 2b 



13. Average Temperature by Months at Repre- 



sentative Points - 27 



14. Frost Free Period at Different Points 20 



15. Temperature Zones of Canada 31 



16. Hours of Possible Sunshine Daily in Summer 3~> 



17. Rock Weathering 39 



18. Soil Surface Map of Iowa 42 



19. Pot Cultures - 47 



20. Illinois Fertilizer Experiment - - 59 



