3o^ 



-/ 



ACKNOWLEDGEMENTS. 



The investigation reported in this thesis was undertaken at the 

 suggestion of Dr. F. J. Alway, to whom the author is indebted for 

 advice and assistance during its progress. Acknowledgement is also 

 made to Mr. W. M. Shaw, who assisted in part of the analytical work. 



C. O. R. 

 University of Minnesota, 

 Division of Soils. 

 May 1, 1918. 



EXcnArsoK 



