Preface xi 



to Prof. F. B. Paddock; to Prof. W. G. Sackett; to 

 Prof. A. D. Selby; to Prof. R. E. Smith; to Prof. H. 

 E. Stevens; to Prof. J. A. Stevenson; to Prof. D. B. 

 Swingle; to Prof. DeVault and to Dr. F. A. Wolf. 



Last, but not least, grateful acknowledgments are 

 due my wife Esther Michla Taubenhaus, whose de- 

 votion to art and science, and whose inspiration made 

 this work possible. 



J. J. Taubenhaus 



College Station, Texas 

 January 22, 1918. 



