REFERENCES 



1. V ENABLE : History of Chemistry. 



2. GILBERT : Inaugural Lecture, University of Oxford. 



3. LIEBIG : Chemistry in Its Applications to Agriculture and 



Physiology. 



4. GILBERT : The Scientific Principles of Agriculture (Lecture). 



5. SNYDER: Minnesota Agricultural Experiment Station Bulletin 



No. 30. 



6. WILEY : Agricultural Analysis, Vol. I. 

 7! HILGARD : Soils. 



8. Maryland Agricultural Experiment Station Bulletin No. 21. 



9. SNYDER : Minnesota Agricultural Experiment Station Bulletin 



No. 41. 



10. OSBORNE : Journal of Analytical Chemistry, Vol. II, Part 3. 



11. Bureau of Soils. Numerous bulletins on soil types. 



12. HELLRIEGEL : Calculated from Beitrage zu den Naturwissen- 



schaft Grandlagen des Ackerbaus. 



13. KING : Wisconsin Agricultural Experiment Station Report, 



1889. 



14. Unpublished results of author. 



15. KING : Soils. 



1 6. ROBERTS : Fertility of the Land. 



17. STOCKBRIDGE : Rocks and Soils. 



18. SNYDER: Minnesota Agricultural Experiment Station Bulletin 



No. 53. 



19. WHITNEY : Division of Soils, U. S. Department of Agriculture 



Bulletin No. 6. 



20. MERRILL : Rocks, Rock-weathering, and Soils. 



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